Validation of data is an important part of web application development. It guarantees that the information submitted by users is correct, safe, and follows the anticipated format. FluentValidation in ASP.NET Core provides a powerful and easy way to handle validation logic, allowing developers to validate user input while maintaining clean, maintainable code.

What is ASP.NET Core FluentValidation?
FluentValidation is a well-known.NET library for creating strongly typed validation rules. FluentValidation, as opposed to traditional attribute-based validation, provides a more expressive syntax and allows developers to construct validation logic in a distinct, clean, and reusable manner. It integrates effortlessly into ASP.NET Core applications, providing a strong solution for validating user input.To begin using FluentValidation, create an ASP.NET Core Web API project.

After you've created the project, you'll need to add two NuGet packages to it.

NuGet\Install-Package FluentValidation -Version 11.7.1
NuGet\Install-Package FluentValidation.DependencyInjectionExtensions -Version 11.7.1

After the installation is complete, you will be able to define validation criteria for the models you generate.

Developing Validation Rules
Consider a straightforward registration form with fields such as username, email, and password. Create a validator class and an associated model to validate this form:

public class UserRegistrationModel
{
    public string Username { get; set; }
    public string Email { get; set; }
    public string Password { get; set; }
}

public class UserRegistrationValidator : AbstractValidator<UserRegistrationModel>
{
    public UserRegistrationValidator()
    {
        RuleFor(x => x.Username).NotEmpty().MinimumLength(3);
        RuleFor(x => x.Email).NotEmpty().EmailAddress();
        RuleFor(x => x.Password).NotEmpty().MinimumLength(6);
    }
}

After the installation is complete, you will be able to define validation criteria for the models you generate.
Developing Validation Rules

Consider a straightforward registration form with fields such as username, email, and password. Create a validator class and an associated model to validate this form:

builder.Services.AddScoped<IValidator<UserRegistrationModel>, UserRegistrationValidator>(); // register validators

Including Validation in Controllers
You can now utilize the validator in your controller to validate the model.

[HttpPost]
  public IActionResult Register(UserRegistrationModel model)
  {
      var validator = new UserRegistrationValidator();
      var validationResult = validator.Validate(model);

      if (!validationResult.IsValid)
      {
          return BadRequest(validationResult.Errors);
      }

      // Process registration logic if the model is valid

      return Ok("Registration successful!");
  }

In this case, the Register action method validated the receiving UserRegistrationModel with UserRegistrationValidator. If the model is invalid, a BadRequest response containing the validation errors is returned.

Please test it with Postman to check that it is working properly. Please let me know if you require any assistance in setting up the test.

The validation appears to be working well now.

FluentValidation streamlines the data validation process in ASP.NET Core apps. Developers can design complicated validation rules in a legible and maintainable manner by providing a fluent and expressive API. You can ensure that your apps process user input accurately and securely by introducing FluentValidation into your ASP.NET Core projects, resulting in a more robust and dependable user experience.

Implementing a complete solution with all of the details you've asked requires a substantial amount of code, and providing an exhaustive example here may not be possible. I can, however, provide a general layout and code snippets for each layer of the Clean Architecture in an ASP.NET Core Web API application using the Facade Pattern for a CarCompany CRUD transaction.
Layers of Architecture that are Clean

Web API (Presentation Layer)
HTTP requests are handled by controllers.
DTOs (Data Transfer Objects) are used to communicate.

// CarCompanyController.cs
[ApiController]
[Route("api/[controller]")]
public class CarCompanyController : ControllerBase
{
    private readonly ICarCompanyFacade _carCompanyFacade;

    public CarCompanyController(ICarCompanyFacade carCompanyFacade)
    {
        _carCompanyFacade = carCompanyFacade;
    }

    [HttpGet]
    public IActionResult GetAll()
    {
        var carCompanies = _carCompanyFacade.GetAllCarCompanies();
        return Ok(carCompanies);
    }

    [HttpGet("{id}")]
    public IActionResult GetById(int id)
    {
        var carCompany = _carCompanyFacade.GetCarCompanyById(id);
        return Ok(carCompany);
    }

    [HttpPost]
    public IActionResult Create([FromBody] CarCompanyDto carCompanyDto)
    {
        var createdCompany = _carCompanyFacade.CreateCarCompany(carCompanyDto);
        return CreatedAtAction(nameof(GetById), new { id = createdCompany.Id }, createdCompany);
    }

    [HttpPut("{id}")]
    public IActionResult Update(int id, [FromBody] CarCompanyDto carCompanyDto)
    {
        _carCompanyFacade.UpdateCarCompany(id, carCompanyDto);
        return NoContent();
    }

    [HttpDelete("{id}")]
    public IActionResult Delete(int id)
    {
        _carCompanyFacade.DeleteCarCompany(id);
        return NoContent();
    }
}

Application Layer

• Interfaces for the Facade.
• Implementation of the Facade.

// ICarCompanyFacade.cs
public interface ICarCompanyFacade
{
    IEnumerable<CarCompanyDto> GetAllCarCompanies();
    CarCompanyDto GetCarCompanyById(int id);
    CarCompanyDto CreateCarCompany(CarCompanyDto carCompanyDto);
    void UpdateCarCompany(int id, CarCompanyDto carCompanyDto);
    void DeleteCarCompany(int id);
}

// CarCompanyFacade.cs
public class CarCompanyFacade: ICarCompanyFacade
{
    private readonly ICarCompanyService _carCompanyService;

    public CarCompanyFacade(ICarCompanyService carCompanyService)
    {
        _carCompanyService = carCompanyService;
    }

    public IEnumerable<CarCompanyDto> GetAllCarCompanies()
    {
        try
        {
            var carCompanies = _carCompanyService.GetAllCarCompanies();
            return carCompanies.Select(MapToDto);
        }
        catch (Exception ex)
        {
            throw new ApplicationException("Error occurred while fetching car companies.", ex);
        }
    }

    public CarCompanyDto GetCarCompanyById(int id)
    {
        try
        {
            var carCompany = _carCompanyService.GetCarCompanyById(id);
            return carCompany != null ? MapToDto(carCompany) : null;
        }
        catch (Exception ex)
        {
            throw new ApplicationException($"Error occurred while fetching car company with Id {id}.", ex);
        }
    }

    public CarCompanyDto CreateCarCompany(CarCompanyDto carCompanyDto)
    {
        try
        {
            var newCompany = new CarCompany
            {
                Name = carCompanyDto.Name,
            };

            _carCompanyService.CreateCarCompany(newCompany);
            return MapToDto(newCompany);
        }
        catch (Exception ex)
        {
            throw new ApplicationException("Error occurred while creating a new car company.", ex);
        }
    }

    public void UpdateCarCompany(int id, CarCompanyDto carCompanyDto)
    {
        try
        {
            var existingCompany = _carCompanyService.GetCarCompanyById(id);

            if (existingCompany != null)
            {
                existingCompany.Name = carCompanyDto.Name;
                // Update other properties...

                _carCompanyService.UpdateCarCompany(existingCompany);
            }
            else
            {
                throw new KeyNotFoundException($"Car company with Id {id} not found.");
            }
        }
        catch (Exception ex)
        {
            throw new ApplicationException($"Error occurred while updating car company with Id {id}.", ex);
        }
    }

    public void DeleteCarCompany(int id)
    {
        try
        {
            var existingCompany = _carCompanyService.GetCarCompanyById(id);

            if (existingCompany != null)
            {
                _carCompanyService.DeleteCarCompany(existingCompany);
            }
            else
            {
                throw new KeyNotFoundException($"Car company with Id {id} not found.");
            }
        }
        catch (Exception ex)
        {
            throw new ApplicationException($"Error occurred while deleting car company with Id {id}.", ex);
        }
    }

    private CarCompanyDto MapToDto(CarCompany carCompany)
    {
        return new CarCompanyDto
        {
            Id = carCompany.Id,
            Name = carCompany.Name,
        };
    }
}

Domain Layer
Define the CarCompany entity.
// CarCompany.cs
public class CarCompany
{
    public int Id { get; set; }
    public string Name { get; set; }
}

Infrastructure Layer
Implement the repository, database context, and any other infrastructure concerns.
// CarCompanyDbContext.cs
public class CarCompanyDbContext: DbContext
{
    public DbSet<CarCompany> CarCompanies { get; set; }

    public CarCompanyDbContext(DbContextOptions<CarCompanyDbContext> options) : base(options)
    {
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        // Configure entity properties, relationships, etc.
        modelBuilder.Entity<CarCompany>().HasKey(c => c.Id);
        modelBuilder.Entity<CarCompany>().Property(c => c.Name).IsRequired();
        // Configure other properties...

        // Seed initial data if needed
        modelBuilder.Entity<CarCompany>().HasData(
            new CarCompany { Id = 1, Name = "Company A" },
            new CarCompany { Id = 2, Name = "Company B" }
            // Add other seed data...
        );

        base.OnModelCreating(modelBuilder);
    }
}

// CarCompanyRepository.cs
public class CarCompanyRepository: ICarCompanyRepository
{
    private readonly CarCompanyDbContext _dbContext;

    public CarCompanyRepository(CarCompanyDbContext dbContext)
    {
        _dbContext = dbContext;
    }

    public IEnumerable<CarCompany> GetAll()
    {
        return _dbContext.CarCompanies.ToList();
    }

    public CarCompany GetById(int id)
    {
        return _dbContext.CarCompanies.Find(id);
    }

    public void Add(CarCompany carCompany)
    {
        _dbContext.CarCompanies.Add(carCompany);
        _dbContext.SaveChanges();
    }

    public void Update(CarCompany carCompany)
    {
        _dbContext.CarCompanies.Update(carCompany);
        _dbContext.SaveChanges();
    }

    public void Delete(int id)
    {
        var carCompany = _dbContext.CarCompanies.Find(id);
        if (carCompany != null)
        {
            _dbContext.CarCompanies.Remove(carCompany);
            _dbContext.SaveChanges();
        }
    }
}

// ICarCompanyRepository.cs
public interface ICarCompanyRepository
{
    IEnumerable<CarCompany> GetAll();
    CarCompany GetById(int id);
    void Add(CarCompany carCompany);
    void Update(CarCompany carCompany);
    void Delete(int id);
}

Dependency Injection
Register dependencies in Startup.cs.

public void ConfigureServices(IServiceCollection services)
{
    services.AddScoped<ICarCompanyRepository, CarCompanyRepository>();
    services.AddScoped<ICarCompanyService, CarCompanyService>();
    services.AddScoped<ICarCompanyFacade, CarCompanyFacade>();
}

The implementation follows Clean Architecture principles in an ASP.NET Core Web API application, using the Facade Pattern to encapsulate the complexity of the CarCompany CRUD activities. The presentation layer, represented by the CarCompanyController, is in charge of handling HTTP requests, whilst the application layer introduces the ICarCompanyFacade interface and its implementation, CarCompanyFacade, which is in charge of orchestrating interactions with the underlying services. The CarCompany object is defined in the domain layer, containing the fundamental business logic, while the infrastructure layer handles data access via the CarCompanyRepository and database context. The Startup.cs file uses dependency injection to connect the various components. This structured method improves maintainability, scalability, and testability, allowing for simple system extension and modification in accordance with Clean Architecture principles. As a starting point, and further improvements can be developed based on unique project requirements.

Microsoft's open-source web framework, ASP.NET Core, provides developers with a versatile and modular platform for developing high-performance web applications. One of the most important components of ASP.NET Core application development is effectively managing dependencies. AddTransient and AddScoped are two often used techniques for registering services in the world of dependency injection, particularly when working with repositories. Choosing between these strategies can have a major impact on your application's behavior and performance. This detailed guide seeks to clarify the distinctions between AddTransient and AddScoped in order to assist developers in making educated decisions when registering repositories in ASP.NET Core apps.

Understanding ASP.NET Core Dependency Injection
DI is a design pattern that encourages loose coupling between components of an application by allowing one object to satisfy the dependencies of another. DI is a critical method in ASP.NET Core for controlling object instantiation and lifespan.

AddTransient: Short-lived Instances
AddTransient is used to register services that are created each time they are requested. In the context of repository registration, this means a new instance of the repository is created every time it is injected into a component such as a controller or a service. Transient services are suitable for lightweight, stateless services or repositories that don’t store any client-specific data.

services.AddTransient<IRepository, Repository>();

AddScoped: Scoped Instances

In contrast, AddScoped generates a single instance of the service for each scope. Each HTTP request generates a scope in the context of web applications. This means that all components sharing the same scoped instance of a service will use the same instance of that service within a single HTTP request. Scoped services are useful for stateful components such as database contexts or repositories that require state to be maintained across several areas of the application within a single request.

services.AddScoped<IRepository, Repository>();

Selecting AddTransient vs. AddScoped

The decision between AddTransient and AddScoped comes down to the desired behavior of your repositories:

When should you use AddTransient?
Statelessness is essential: Using AddTransient is useful if your repository is stateless and does not save any data between method calls. Each method call is assigned a repository instance.
Transient services are appropriate for lightweight operations when the expense of producing a new instance is small in comparison to the benefits of having a fresh instance each time.

Use AddScoped When:
Stateful Operations: If your repository or service maintains state throughout the duration of an HTTP request, using AddScoped ensures that all parts of your application that need the repository within the same request share the same instance.
Database Contexts: When dealing with Entity Framework Core’s DbContext, using AddScoped is crucial. DbContext instances should typically be scoped to the lifetime of a request to ensure data consistency and proper unit of work pattern.

Performance and Memory Usage Considerations
AddTransient is often faster in terms of performance because it does not use tracking scopes. However, in most situations, the difference may be minimal, and the ease and safety afforded by AddScoped frequently outweigh any minor performance improvements.

In terms of memory utilization, AddTransient can cause a greater number of instances to be created, thereby straining memory resources, particularly in high-traffic applications. AddScoped can improve memory usage by reusing instances inside the scope of a request.

The choice between AddTransient and AddScoped for repository registration in ASP.NET Core is determined by your application's individual requirements and characteristics. Understanding the fundamental distinctions and consequences of these technologies is critical for developing efficient, high-performance, and maintainable online applications. You can ensure that your services and repositories operate as intended by selecting the proper lifespan method, resulting in a seamless user experience and optimal resource use.

Dependency injection is a technique for getting a dependant object from somewhere other than the class that was created with the new keyword.

Pros

• It improved modularity.
• It boosts testability.
• Place the dependent in a central location.
• Uncouple the system

The dependency injection (DI) software design pattern, which is a mechanism for accomplishing Inversion of Control (IoC) between classes and their dependencies, is supported by ASP.NET Core.

• Constructor Injection: The most common method of injecting dependencies into a class by giving them as constructor parameters.
• Method Injection is the process of injecting dependencies into a method as parameters.
• Property Injection is the process of populating a class's properties with the necessary dependencies.

We must provide the dependency's lifespan when we register it with DI Container (IServiceCollection).

Service Duration
The service lifetime determines how long an object lives once it is generated by the container. When registering, use the following method on the IServiceColletion to create the lifetime.

• Services are transient since they are produced each time they are requested.
• For example, with transitory tea makers, each customer gets a different tea. They get a one-of-a-kind tea experience because a new tea maker arrives for each order and serving.
• Services are created just once per request.
• In a teashop, for example, scored tea makers are equivalent to having one tea maker assigned to each table or group, giving the same type of tea to everyone within the group. When a new group arrives, they are assigned a tea maker.
• Singleton: A service is created only once for the duration of the program. For example, having a singleton tea maker in a teashop is equivalent to having a renowned tea master who provides the same tea to every customer. This tea master is constantly there, remembers all orders, and regularly serves everyone the same tea.

Let's now dive into the code to further explain this concept.

TeaService
public class TeaService : ITeaService
{
        private readonly int _randomId ;
        private readonly Dictionary<int, string> _teaDictionary = new()
        {
            { 1, "Normal Tea ☕️" },
            { 2, "Lemon Tea ☕️" },
            { 3, "Green Tea ☕️" },
            { 4, "Masala Chai ☕️" },
            { 5, "Ginger Tea ☕️" }
        };
 public TeaService()
 {
      _randomId = new Random().Next(1, 5);
  }
  public string GetTea()
   {
      return _teaDictionary[_randomId];

    }
}
public interface ITeaService
{
        string GetTea();
}

RestaurantService: which injects TeaService.
public class RestaurantService : IRestaurantService
{
        private readonly ITeaService _teaService;
        public RestaurantService(ITeaService teaService)
        {
            _teaService = teaService;
        }

        public string GetTea()
        {
            return _teaService.GetTea();
        }
}
public interface IRestaurantService
{
     string GetTea();
 }

Tea Controller: which is injecting TeaService and RestaurantService.
[Route("api/[controller]")]
[ApiController]
public class TeaController : ControllerBase
{
  private readonly ITeaService _teaService;
  private readonly IRestaurantService _restaurantService;

  public TeaController(ITeaService teaService,
   IRestaurantService restaurantService)
  {
      _teaService = teaService;
      _restaurantService = restaurantService;
   }

   [HttpGet]
   public IActionResult Get()
   {
      var tea = _teaService.GetTea();
      var teaFromRestra = _restaurantService.GetTea();
      return Ok($"From TeaService : {tea}
               \nFrom RestaurantService : {teaFromRestra}");
    }
}

Register services to DI Container.

a. Transient
// Add the below line to configure service in Statup.cs
services.AddTransient<ITeaService, TeaService>();
services.AddTransient<IRestaurantService, RestaurantService>();

Output

b. Scoped
// Add the below line to configure service in Statup.cs
services.AddScoped<ITeaService, TeaService>();
services.AddScoped<IRestaurantService, RestaurantService>();

Output

c: Singleton
// Add the below line to configure service in Statup.cs
services.AddSingleton<ITeaService, TeaService>();
services.AddSingleton<IRestaurantService, RestaurantService>();

Output

Pattern matching is a functional programming feature that is already present in several prominent languages, including Scala, Rust, Python, Haskell, Prolog, and others. It is used to test expressions for certain circumstances while also testing the kinds.

It enables you to check if a value matches a specific pattern and then execute code based on that match in an efficient and simple manner. This capability is very handy when working with complex data structures like collections and when simplifying conditional expressions.

Pattern Matching was introduced in C# 7.

Benefits- Patterns Matching

• Type-Testing
• Nullable-type checking
• Typecasting and assignment
• High readability
• Concise syntax Less convoluted code.

Usages
Pattern matching can be used in 2 places.
'is' expressions
'switch' expressions

Patterns Matching Types through C# Versions

C# 7
Type Pattern
Declaration Pattern
Constant Pattern
Null Pattern
Var Pattern

C# 8
Property Pattern
Discard Pattern
Positional Pattern
Discard Pattern

C# 9
Type Pattern
Relative Pattern
Logical Pattern (Combinators)
Negated Null Constant Pattern
Parenthesized Pattern

C# 10
Extended Property Pattern

C# 11
List Pattern

Type Pattern
A type pattern in C# allows you to check whether an object is of a specific type and, if it is, cast it to that type while declaring a new variable.

using System;

public class Program
{
    public static void Main()
    {
        object someObject = "Hello, World!";

        if (someObject is string stringValue)
        {
            // stringValue is now a strongly-typed variable of type string
            Console.WriteLine($"Length of the string: {stringValue.Length}");
        }
        else
        {
            Console.WriteLine("someObject is not a string.");
        }
    }
}

Pattern of Declaration
In C#, a declaration pattern is one that not only examines whether an expression matches a given pattern but also declares a new variable with the matched value. This pattern is frequently used in conjunction with is expressions to accomplish pattern matching as well as variable declaration in a single action.

C# 7.0 added declaration patterns, which provided a handy approach to simplify code.

using System;

public class Program
{
    public static void Main()
    {
        object someObject = 42;

        if (someObject is int intValue)
        {
            // intValue is now a strongly-typed variable of type int
            Console.WriteLine($"The value is an integer: {intValue}");
        }
        else
        {
            Console.WriteLine("The value is not an integer.");
        }
    }
}

Recurring pattern
Testing against a constant value, which can be an int, float, char, string, bool, enum, const-declared field, or null.
It's frequently used in switch statements and pattern-matching contexts to conduct different actions based on an expression's value.

using System;

public class Program
{
    public static void Main()
    {
        object someObject = 42;

        if (someObject is int intValue)
        {
            // intValue is now a strongly-typed variable of type int
            Console.WriteLine($"The value is an integer: {intValue}");
        }
        else
        {
            Console.WriteLine("The value is not an integer.");
        }
    }
}

Null Pattern
Check if a reference or nullable type is null.
It is particularly useful for safely handling null values and reducing null reference exceptions.
Null pattern matching was introduced in C# 9.0 as part of the language's pattern-matching enhancements.

Var Pattern
Similar to the type pattern, the var pattern matches an expression and checks for null, as well as assigns a value to the variable.

The var type is declared based on the matched expression’s compile-time type.

using System;

public class Program
{
    public static void Main()
    {
        object someObject = (42, "Hello, Peter!");

        if (someObject is var (number, message) && number is int && message is string)
        {
            Console.WriteLine($"Number: {number}, Message: {message}");
        }
        else
        {
            Console.WriteLine("Pattern match failed.");
        }
    }
}

Property Pattern
Property pattern matching in C# is a feature that allows you to match objects based on the values of their properties or fields.
It simplifies code by enabling you to specify patterns that involve property values directly in pattern-matching expressions.
Property pattern matching was introduced in C# 8.0 and is a powerful way to work with complex data structures.
using System;

public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public class Program
{
    public static void Main()
    {
        Person person = new Person { Name = "Alice", Age = 30 };

        if (person is { Name: "Alice", Age: 30 })
        {
            Console.WriteLine("It's Alice, age 30!");
        }
        else
        {
            Console.WriteLine("It's someone else.");
        }
    }
}

Discard Pattern
discard pattern in C# allows you to match a pattern but discard the matched value.
It's represented by the underscore (_) and is especially useful when you want to indicate that you're not interested in the value that matches a pattern, which can help improve code clarity and readability. Discard patterns were introduced in C# 7.0.

using System;

public class Program
{
    public static void Main()
    {
        object someObject = "Hello, World!";

        if (someObject is string _)
        {
            Console.WriteLine("The object is a string, but we're not interested in its value.");
        }
        else
        {
            Console.WriteLine("The object is not a string.");
        }
    }
}

Positional Pattern
Positional patterns in C# allow you to match objects based on the values of their elements in a specific order, making it easier to work with complex data structures like arrays, tuples, or user-defined types.
This feature was introduced in C# 8.0 and provides a concise way to match objects by their elements' positions.

using System;

public class Program
{
    public static void Main()
    {
        Point point = new Point(3, 4);

        string location = DescribePoint(point);

        Console.WriteLine(location);
    }

    public static string DescribePoint(Point point)
    {
        return point switch
        {
            (0, 0) => "The point is at the origin (0, 0).",
            (var x, var y) when x == y => $"The point is on the diagonal at ({x}, {y}).",
            (var x, var y) => $"The point is at ({x}, {y}).",
            _ => "Unknown location."
        };
    }
}

public record Point(int X, int Y);

Tuple Pattern
Tuple patterns in C# allow you to match objects against specific tuple structures. This feature simplifies the process of deconstructing and matching tuples in pattern-matching expressions.
Tuple patterns were introduced in C# 8.0 and make it easier to work with complex data structures involving tuples.

using System;

public class Program
{
    public static void Main()
    {
        var point = (3, 4);

        string location = DescribePoint(point);

        Console.WriteLine(location);
    }

    public static string DescribePoint((int X, int Y) point)
    {
        return point switch
        {
            (0, 0) => "The point is at the origin (0, 0).",
            (_, 0) => "The point is on the x-axis.",
            (0, _) => "The point is on the y-axis.",
            var (x, y) when x == y => $"The point is on the diagonal at ({x}, {y}).",
            var (x, y) => $"The point is at ({x}, {y}).",
        };
    }
}

var person = ("Alice", 30);

var description = person switch
{
    ("Alice", 30) => "This is Alice, age 30.",
    ("Bob", var age) => $"This is Bob, age {age}.",
    _ => "Unknown person."
};

C#
 ‘Enhanced’ Type Pattern

    You can do type checking in switch expressions without using the discards with each type

public string CheckValueType(object value)=> value switch
{
  int => "integer number",
  decimal => "decimal number",
  double => "double number",
  _ => throw new InvalidNumberException(value)
};

Pattern matching is a powerful feature in C# that simplifies code by allowing you to match objects and structures based on patterns. Whether you're checking types, values, or even properties, pattern matching makes your code more concise and readable.

Pattern matching in C# streamlines your code, reduces errors, and enhances readability, making it a valuable tool for developers.

This tutorial will teach us about the NavigationPage in.NET MAUI. If you are new to MAUI, I recommend that you read the articles in this series listed below. One of the most important components of developing an application is navigation. The NavigationPage class in.NET MAUI provides a hierarchical navigation experience for navigating through pages. The navigation is provided as a LIFO (Last-In, First-Out) stack of page objects by NavigationPage. To demonstrate, I'll add three ContentPages to the.NET MAUI project and demonstrate how to navigate from one page to the next. The most frequent page type in.NET MAUI is the ContentPage, which is a single view, and a single.NET MAUI application can contain numerous pages derived from the ContentPage.

Let's create three.NET MAUI ContentPages (XAML) in a.NET MAUI project. I called the three ContentPages HomePage, ProductPage, and ProductDetails page.

A root page is required for every app with several pages. Now, let's make the HomePage the Navigation stack's root page. To accomplish this, we must associate the App.Main page property with the NavigationPage object, which constructor accepts the root page as a parameter, i.e. the App's HomePage.

Now, add a button (named btnGoToProductPage) to navigate from the HomePage to ProductPage.

HomePage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="NavigationPageDemo.HomePage"
             Title="Home Page">
    <VerticalStackLayout>
        <Label Text="Home Page Content"
               VerticalOptions="Center"
               HorizontalOptions="Center"
               Margin="10" />
        <Button x:Name="btnGoToProductPage"
                Text="Go to Product Page"
                Clicked="btnGoToProductPage_Clicked"
                Margin="10" />
    </VerticalStackLayout>
</ContentPage>

A page can be navigated by calling the PushAsync method on the Navigation property of the Current Page. In the below example, ProductPage is pushed onto the Navigation stack where it becomes the active page.

HomePage.xaml.cs
using System;
using Microsoft.Maui.Controls;
namespace NavigationPageDemo
{
    public partial class HomePage : ContentPage
    {
        public HomePage()
        {
            InitializeComponent();
        }
        private void btnGoToProductPage_Clicked(object sender, EventArgs e)
        {
            Navigation.PushAsync(new ProductPage());
        }
    }
}

In ProductPage, I have added two buttons named “btnGoToProductDetails” and ”btnGoBackToHomePage”. On clicking on btnGoToProductDetails, the ProductDetails page will be added to the navigation stack, and it will become the active page. On clicking on btnGoBackToHomePage, the PopAsync method will remove the current page i.e., Product Page, from the navigation stack, and the topmost page of the stack will become the active page.

ProductPage.xaml
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="NavigationPageDemo.ProductPage"
             Title="Product Page">
    <VerticalStackLayout>
        <Label Text="Product Page"
               VerticalOptions="Center"
               HorizontalOptions="Center"
               Margin="10" />
        <Button x:Name="btnGoToProductDetails"
                Text="Go to Product Details"
                Clicked="btnGoToProductDetails_Clicked"
                Margin="10" />
        <Button x:Name="btnGoBackToHomePage"
                Text="Go back to Home Page"
                Clicked="btnGoBackToHomePage_Clicked"
                Margin="10" />
    </VerticalStackLayout>
</ContentPage>

ProductPage.xaml.cs
using System;
using Microsoft.Maui.Controls;
namespace NavigationPageDemo
{
    public partial class ProductPage : ContentPage
    {
        public ProductPage()
        {
            InitializeComponent();
        }
        private void btnGoToProductDetails_Clicked(object sender, EventArgs e)
        {
            Navigation.PushAsync(new ProductDetails());
        }
        private void btnGoBackToHomePage_Clicked(object sender, EventArgs e)
        {
            Navigation.PopAsync();
        }
    }
}

On the ProductDetails Page, I have added a button i.e. btnGoBackToProductPage. On Clicking, it will remove the current page from the navigation stack with the PopAsync method call.

ProductDetails.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="NavigationPageDemo.ProductDetails"
             Title="Product Details">
    <VerticalStackLayout>
        <Label Text="Product Details"
               VerticalOptions="Center"
               HorizontalOptions="Center"
               Margin="10" />
        <Button x:Name="btnGoBackToProductPage"
                Text="Go back to Product Page"
                Clicked="btnGoBackToProductPage_Clicked"
                Margin="10" />
    </VerticalStackLayout>
</ContentPage>

ProductDetails.xaml.cs

using System;
using Microsoft.Maui.Controls;
namespace NavigationPageDemo
{
    public partial class ProductDetails : ContentPage
    {
        public ProductDetails()
        {
            InitializeComponent();
        }
        private void btnGoBackToProductPage_Clicked(object sender, EventArgs e)
        {
            Navigation.PopAsync();
        }
    }
}

Working Preview on Android

Preview on Windows

The navigation property of the page also provides the InsertPageBefore and RemovePage methods for manipulating the Stack by inserting the pages or removing them.

.NET MAUI also supports Modal navigation. A modal page encourages users to complete a self-contained task that cannot be navigated away until the task is completed or canceled. PushModalAsync and PopModalAsync are the methods to push and pop pages from the modal stack.

NavigationPage has several properties; a few are listed below. (For more details, you can refer to the documentation on Microsoft's official website)
1. BarBackgroundColor: Specifies the background color of the Navigation Bar.
2. BarTextColor: Specifies the Text color of the Navigation Bar
3. HasNavigationBar: Specifies whether a navigation bar is present on the NavigationPage. Its default value is true.
4. HasBackButton: Represent whether the navigation bar includes the back button. The default value of this property is true.

Let’s try to change the navigation bar and text color. Use the below code in the App class; we can change the BarBackground and BarTextColor.

Preview on Android

Preview on Windows

We will look at how to build a powerful console application for sending bulk emails with the latest ASP.NET Core 7.0 framework and smtp server. Businesses frequently want a streamlined approach to send emails to a big number of recipients due to the ever-increasing necessity for effective communication. You will learn how to use the features of ASP.NET Core 7.0 to create a dependable bulk email sending solution by following this step-by-step guide.

Step 1: Install Any Necessary Software
Make sure your system has Visual Studio Community 2022 and SQL Server Management Studio (SSMS) installed. You can get them through Microsoft's official websites.

Step 2. Create a New Console Application

• Navigate to Visual Studio Community 2022.
• Select "Create a new project."
• Search for "Console" in the "Create a new project" dialog's search field.
• Choose "Console App (.NET Core)" as the template.
• Give your project a name and a location, then click "Create."

3. Launch SQL Server Management Studio.

• On your computer, launch SQL Server Management Studio.
• Connect to your SQL Server instance by using the proper server name and authentication method (Windows or SQL Server).

Step 4: Make a New Database.

• Right-click on "Databases" in the Object Explorer window and select "New Database."
• In the "New Database" window, in the "Database name" area, provide a name for your database.
• If necessary, configure other parameters such as data file locations.
• To build the database, click the "OK" button.

Here's an example

CREATE DATABASE bulkEmailDemoDB;

Step 5. Create a New TableExpand the newly created database in the Object Explorer window.Right-click on "Tables" within your database, and then select "New Table."In the

Table Designer window:
Define the columns for your table. For each column, specify a name, data type, length (if applicable), and other properties.
Click the "Save" icon (or press Ctrl + S) to save the table.
Provide a name for your table and click the "OK" button to create it.

Here's an example
Choose the table name as per your requirement
CREATE TABLE ClientMailReminder (
    ClientCode VARCHAR(255),
    EmailId VARCHAR(255) NOT NULL,
    PhoneNumber VARCHAR(20) NOT NULL,
    Status VARCHAR(50)
);

Now insert the dummy data for demo purposes. In your table, you can insert genuine record
INSERT INTO ClientMailReminder (ClientCode, EmailId, PhoneNumber, Status)
VALUES
    ('CLNT001', '[email protected]', '1234567890', 'Active'),
    ('CLNT002', '[email protected]', '9876543210', 'Inactive'),
    -- ... (continue for the remaining records)
    ('CLNT020', '[email protected]', '5555555555', 'Active');

Create a model class.
public class ClientMailRemainder
{
    public string? ClientCode { get; set; }
    public string EmailId { get; set; }
    public string PhoneNumber { get; set; }
    public string? Status { get; set; }
}

Let's Install Required NuGet Packages:
    Microsoft.EntityFrameworkCore
    Microsoft.EntityFrameworkCore.SqlServer

Create BulkEmailContext Class:
Next, create a class named BulkEmailContext that inherits from DbContext. This class represents your database context and provides the DbSet properties for your entities.
using Microsoft.EntityFrameworkCore;

public class BulkEmailContext : DbContext
{
    public BulkEmailContext(DbContextOptions<BulkEmailContext> options) : base(options)
    {
    }

    // DbSet properties for your entities
    public DbSet<ClientMailReminder> ClientMailReminders { get; set; }

}

Configure Program.cs (for ASP.NET Core 7.0):
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;

namespace Yournamespace;

class Program
{

    static async Task Main(string[] args)
    {
        HostApplicationBuilder builder = Host.CreateApplicationBuilder(args);

        var options = new DbContextOptionsBuilder<EmailDbContext>().UseSqlServer("your connection string").Options;
        using (var context = new EmailDbContext(options)) // Create your EmailDbContext instance
        {
            await BulkEmail.GetEmailAsync(context); // Call the static method

            Console.WriteLine("Bulk email and mobile sending completed."); // Optional: Print a message
        }



    }
}

Create a BulkEmail.cs file
public static async Task GetEmailAndMobileNumberAsync(EmailDbContext context)
{
    var activeUserEmails = await _context.ClientMailRemainder
    .Where(e => e.Status == "Active")
    .Select(e => e.EmailId)
    .ToListAsync();

    string subject = " DotNet Reminder";
    string content = "<html><body>DotNet meetup reminder</body></html>";
    List<string> emailRecipients = activeUsers.Select(user => user.Email).ToList();
    int counts = context.ClientMailRemainder.Count();
    await SendEmailsInBatchesAsync(counts, emailRecipients, subject, content);
}

Implementing SendEmailsInBatchesAsync method
public static async Task SendEmailsInBatchesAsync(int count,List<string> emailAddresses, string subject, string content, int batchSize = 100)
{
    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls13;

    var smtpClients = new List<SmtpClient>();

    // Determine the total number of rows in the database table
    int totalRowCount = count; // To count table record

    // Calculate the number of batches needed
    int totalBatches = (int)Math.Ceiling((double)totalRowCount / batchSize);

    for (int i = 0; i < totalBatches; i++)
    {
        SmtpClient smtpClient = new SmtpClient("your");
        smtpClient.Port = 587;
        smtpClient.Credentials = new NetworkCredential("your", "your");
        smtpClients.Add(smtpClient);
    }

    var tasks = new List<Task>();

    int emailsSentCount = 0;

    for (int batchIndex = 0; batchIndex < totalBatches; batchIndex++)
    {
        var batch = emailAddresses.Skip(batchIndex * batchSize).Take(batchSize).ToList();
        int startIndex = batchIndex * batchSize;

        tasks.Add(Task.Run(async () =>
        {
            int clientIndex = startIndex / batchSize;

            using (var client = smtpClients[clientIndex])
            {
                for (int j = 0; j < batch.Count; j++)
                {
                    var emailAddress = batch[j];
                    var clientCode = clientCodes[startIndex + j];

                    using (var message = new MailMessage())
                    {
                        message.From = new MailAddress("your");
                        message.Subject = subject;
                        message.Body = content;
                        message.IsBodyHtml = true;
                        message.To.Add(emailAddress);

                        try
                        {
                            await client.SendMailAsync(message);
                            Interlocked.Add(ref emailsSentCount, 1);
                            Console.WriteLine($"Email sent successfully to: {emailAddress}");
                            //emailsSentCount++;
                            Console.WriteLine($"Total emails sent: {emailsSentCount}");
                        }
                        catch (Exception ex)
                        {
                            Console.WriteLine($"An error occurred while sending email to {emailAddress}: {ex.Message}");
                        }
                    }
                }
            }
        }));
    }

    await Task.WhenAll(tasks);

    // Dispose all SmtpClient instances
    foreach (var client in smtpClients)
    {
        client.Dispose();
    }
}

The formula (int)Math.Ceiling((double)totalRowCount / batchSize) calculates how many batches you'll need, ensuring you round up to cover all emails.

Loop Through Batches and Initialize SMTP Clients
The code then enters a loop that runs for the total number of batches calculated. Inside the loop, an instance of the SmtpClient class is created and configured for each batch. we are  attempting to distribute the work of sending emails among multiple SMTP clients (perhaps to parallelize the process),

Inside the Task.Run delegate, the code manages sending emails within a batch. It gets the SMTP client based on the batch index, iterates through the batch of email addresses, and sends emails.

The Interlocked.Add(ref emailsSentCount, 1); line ensures that the emailsSentCount is incremented in a thread-safe manner, as multiple tasks might be updating it simultaneously.
 await Task.WhenAll(tasks); waits for all the asynchronous email sending tasks to complete before moving on.

After all the email sending tasks have completed, the code disposes of the SMTP client instances to release resources.

In this post, we will look at the best techniques for increasing the speed of your.NET core application.

It is critical to optimize the performance of your.NET Core application to ensure that it provides a responsive and efficient user experience. Here are some suggested practices for optimizing the performance of your.NET Core application:

1. Make Use of Profiling Tools
Profiling tools like as Visual Studio Profiler, JetBrains dotTrace, and PerfView can assist you in locating bottlenecks and performance issues in your code.
Using a stopwatch to measure method performance is an example.
using System;
using System.Diagnostics;

class Program
{
    static void Main(string[] args)
    {
        Stopwatch stopwatch = new Stopwatch();
        stopwatch.Start();

        // Code to profile

        stopwatch.Stop();
        Console.WriteLine($"Elapsed Time: {stopwatch.ElapsedMilliseconds} ms");
    }
}

2. Caching
Implement caching for frequently accessed data to reduce database load and improve response times. .NET Core has a variety of caching methods, including as in-memory caching and distributed caching using libraries such as Memory Cache or Redis.

Example: Using MemoryCache for in-memory caching.

using System;
using Microsoft.Extensions.Caching.Memory;

class Program
{
    static void Main(string[] args)
    {
        IMemoryCache cache = new MemoryCache(new MemoryCacheOptions());

        // Store data in cache
        cache.Set("myKey", "myValue", TimeSpan.FromMinutes(10));

        // Retrieve data from cache
        if (cache.TryGetValue("myKey", out string value))
        {
            Console.WriteLine($"Cached Value: {value}");
        }
    }
}

3. Database Optimization
Optimize your database queries using proper indexing, query optimization techniques, and stored procedures.
Implement connection pooling to reuse database connections and reduce overhead.

Example: Using proper indexing in Entity Framework Core.

using System;
using System.Linq;
using Microsoft.EntityFrameworkCore;

class Program
{
    static void Main(string[] args)
    {
        var options = new DbContextOptionsBuilder<MyDbContext>()
            .UseSqlServer(connectionString)
            .Options;

        using (var context = new MyDbContext(options))
        {
            // Apply indexing to optimize queries
            var results = context.Orders.Where(o => o.CustomerId == 123).ToList();
        }
    }
}

4. Asynchronous Programming
Use asynchronous programming (async/await) to offload CPU-bound work and improve responsiveness, especially in I/O-bound scenarios.
Utilize asynchronous database drivers and libraries for improved database performance.

Example: Using async/await to perform I/O-bound tasks asynchronously.
using System;
using System.Net.Http;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        using (HttpClient client = new HttpClient())
        {
            HttpResponseMessage response = await client.GetAsync("https://example.com");
            string content = await response.Content.ReadAsStringAsync();
            Console.WriteLine(content);
        }
    }
}

5. Use Entity Framework Core Wisely
If you're using Entity Framework Core for database access, be mindful of the queries it generates. Use eager loading, projections, and optimizations like compiled queries.

Example: Using compiled queries in Entity Framework Core.

using System;
using System.Linq;
using Microsoft.EntityFrameworkCore;

class Program
{
    static void Main(string[] args)
    {
        var options = new DbContextOptionsBuilder<MyDbContext>()
            .UseSqlServer(connectionString)
            .Options;

        using (var context = new MyDbContext(options))
        {
            var compiledQuery = EF.CompileQuery((MyDbContext db, int customerId) =>
                db.Orders.Where(o => o.CustomerId == customerId).ToList());

            var results = compiledQuery(context, 123);
        }
    }
}

6. Memory Management
Minimize object allocations and memory usage. Use value types where appropriate and be cautious with large object graphs.
Utilize the Dispose pattern or use statements for resources like database connections or streams to ensure timely cleanup.
Example: Disposing resources using the Dispose pattern.

using System;

class MyResource : IDisposable
{
    private bool disposed = false;

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        if (!disposed)
        {
            if (disposing)
            {
                // Release managed resources
            }

            // Release unmanaged resources

            disposed = true;
        }
    }

    ~MyResource()
    {
        Dispose(false);
    }
}

7. HTTP Caching
Leverage HTTP caching mechanisms (ETags, Last-Modified headers) to reduce unnecessary data transfers in web applications.
Example: Adding caching headers to HTTP responses.

using Microsoft.AspNetCore.Mvc;
public class MyController : Controller
{
    [HttpGet]
    [ResponseCache(Duration = 300)] // Cache for 5 minutes
    public IActionResult Index()
    {
        // Generate and return response
    }
}

8. Minimize Round-Trips
Reduce the number of HTTP requests and database round-trips. Combine multiple requests when possible.
Example: Combining multiple database queries into a single query.

using System;
using System.Linq;
using Microsoft.EntityFrameworkCore;

class Program
{
    static void Main(string[] args)
    {
        var options = new DbContextOptionsBuilder<MyDbContext>()
            .UseSqlServer(connectionString)
            .Options;

        using (var context = new MyDbContext(options))
        {
            var orders = context.Orders
                .Include(o => o.Customer)
                .Include(o => o.Products)
                .Where(o => o.CustomerId == 123)
                .ToList();
        }
    }
}

9. Content Delivery Networks (CDNs)
Offload static assets (CSS, JavaScript, images) to CDNs for faster delivery to users.
Example: Using a CDN for delivering static assets.

<!-- Link to static asset on CDN -->
<link rel="stylesheet" href="https://cdn.example.com/styles.css">

10. Compression
Enable GZIP or Brotli compression for HTTP responses to reduce data transfer size.
Example: Enabling GZIP compression for HTTP responses.

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.ResponseCompression;

public void ConfigureServices(IServiceCollection services)
{
    services.AddResponseCompression(options =>
    {
        options.EnableForHttps = true;
        options.Providers.Add<GzipCompressionProvider>();
    });
}

11. Logging and Tracing
Use logging levels wisely. Avoid excessive logging in production.
Implement distributed tracing to monitor performance across microservices.

Example: Using a distributed tracing library for monitoring.
using Microsoft.ApplicationInsights;
using Microsoft.ApplicationInsights.Extensibility;

var configuration = TelemetryConfiguration.Active;
var telemetryClient = new TelemetryClient(configuration);

using (var operation = telemetryClient.StartOperation<RequestTelemetry>("MyOperation"))
{
// Perform operation

operation.Telemetry.Success = true;
}

12. Code Analysis and Reviews
Regularly review your codebase for performance issues. Use tools like ReSharper or SonarQube for static code analysis.

code analysis and reviews are essential practices for identifying and addressing code quality, maintainability, and performance issues in your .NET Core application. Code analysis involves using automated tools and manual inspection to review your codebase for potential problems, while code reviews involve the collaborative evaluation of code changes by your development team.

Here's a more detailed explanation of code analysis and reviews:

Code Analysis
Code analysis involves using specialized tools to automatically scan your codebase for potential issues, violations of coding standards, and best practices. These tools can help identify bugs, security vulnerabilities, performance bottlenecks, and other code quality concerns.

Benefits of Code Analysis
Consistency: Code analysis enforces coding standards, ensuring a consistent codebase across your application.
Early Detection: It helps catch issues early in the development process, reducing the likelihood of bugs reaching production.
Efficiency: Automated tools can quickly identify common issues, saving time during manual reviews.
Maintainability: Code analysis improves the long-term maintainability of your application by identifying areas that might become problematic.

Example (Using Roslyn Code Analysis)
The Roslyn compiler platform includes built-in analyzers that can be used to perform code analysis in Visual Studio. You can install additional analyzers from NuGet packages.

Example: Applying code analysis recommendations with ReSharper.
// Example of a code analysis warning

public class ExampleClass
{
public void DoSomething(string input)
{
    if (input == null) // CA1062: Validate arguments of public methods
    {
        throw new ArgumentNullException(nameof(input));
    }

    // Code logic
}
}

13. Parallelism and Concurrency
Utilize parallelism and multithreading for CPU-bound tasks using Parallel class or Task Parallel Library (TPL).
Be cautious with thread synchronization to avoid deadlocks and contention.
Example: Using parallelism for CPU-bound tasks.

Parallel.For(0, 10, i =>
{
// Perform parallelized work
});

14. Resource Optimization
Optimize images and assets for the web to reduce load times.
Minimize the number of external dependencies and libraries.

Example: Optimizing images for the web.
<!-- Optimized image tag -->
<img src="images/my-image.jpg" alt="My Image">

15. Benchmarking and Load Testing
Perform benchmarking and load testing to identify performance bottlenecks and determine how your application performs under different loads.

Benchmarking involves measuring the performance of specific components or functions, while load testing simulates various levels of user traffic to evaluate how well your application handles the load. Both practices help identify bottlenecks, scalability issues, and potential improvements.

Here's a more detailed explanation of benchmarking and load testing:

Benchmarking
Benchmarking involves running specific tests on critical parts of your application to measure their performance. The goal is to establish a baseline and identify areas for improvement. For example, you might benchmark a specific algorithm, database query, or code snippet to compare different implementations and determine which one performs better.

Steps for Benchmarking

• Identify the specific component, function, or operation you want to benchmark.
• Design a set of controlled tests that exercise the component under different scenarios.
• Measure and record performance metrics such as execution time, memory usage, CPU utilization, etc.
• Analyze the results and identify opportunities for optimization.

Example: Using a load testing tool to simulate traffic.

Benchmarking an Algorithm
public class AlgorithmBenchmark
{
public void RunBenchmark()
{
    Stopwatch stopwatch = new Stopwatch();

    stopwatch.Start();

    // Run the algorithm multiple times and measure the time taken
    for (int i = 0; i < 10000; i++)
    {
        // Call the algorithm being benchmarked
        SomeAlgorithm.Perform();
    }

    stopwatch.Stop();

    Console.WriteLine($"Time taken: {stopwatch.ElapsedMilliseconds} ms");
}
}

16. Deployment and Infrastructure
Use containerization (Docker) to ensure consistent deployment environments.
Leverage cloud services and auto-scaling for handling varying traffic loads.
Example: Deploying an application using Docker.

17. Regular Updates
Keep your dependencies, frameworks, and libraries up to date to benefit from performance improvements and bug fixes.
Example: Keeping NuGet packages up to date.

18. Code Profiling and Performance Monitoring
Continuously monitor your application's performance in production using tools like Application Insights, New Relic, or Dynatrace.
Example: Integrating Application Insights for monitoring.
using Microsoft.ApplicationInsights;
using Microsoft.ApplicationInsights.Extensibility;

var configuration = TelemetryConfiguration.Active;
var telemetryClient = new TelemetryClient(configuration);

// Track custom telemetry events
telemetryClient.TrackEvent("CustomEventName");

Here are some additional tips

• Use the latest version of .NET Core.
• Use a lightweight framework.
• Use a good IDE.
• Write clean and well-structured code.
• Use a debugger to find and fix performance problems.
• Monitor the application's performance and make changes as needed.

Remember that the specific optimizations needed for your application may vary based on its nature and requirements. It's important to profile, measure, and test your application to ensure that the changes you make have a positive impact on its performance.

This post will show you how to use Visual Studio Community 2022 to construct a Document Viewer in an Asp.Net Core 7.0 application.

What exactly is GroupDocs.Viewer?
GroupDocs.Viewer is a document viewing and rendering package created by GroupDocs, a business that specializes in document manipulation and conversion APIs for.NET and Java. GroupDocs.Viewer is intended to assist developers in incorporating document viewing capabilities into their applications, allowing users to read a variety of documents right within the application's interface without the need to download or open them with other software.

Let's get started with the document viewer.
In _Layout.html, import the bootstrap 5 cdn.

Install the Nuget Package GroupDocs.Viewer

Make a fresh ASP.NET CORE MVC project.
DocumentViewer.Application is the name of the project.
In the DocumentViewer.Application project, add a new controller.

public class DocViewerController : Controller
{
    private readonly IHostingEnvironment _hostingEnvironment;
    private string projectRootPath;
    private string outputPath;
    private string storagePath;
    List<string> lstFiles;

    public DocViewerController(IHostingEnvironment hostingEnvironment)
    {
        _hostingEnvironment = hostingEnvironment;
        projectRootPath = _hostingEnvironment.ContentRootPath;
        outputPath = Path.Combine(projectRootPath, "wwwroot/Content");
        storagePath = Path.Combine(projectRootPath, "storage");
        lstFiles = new List<string>();
    }

    public IActionResult Index()
    {
        var files = Directory.GetFiles(storagePath);
        foreach (var file in files)
        {
            lstFiles.Add(Path.GetFileName(file));
        }
        ViewBag.lstFiles = lstFiles;
        return View();
    }
    [HttpPost]
    public IActionResult OnPost(string FileName)
    {
        int pageCount = 0;
        string imageFilesFolder = Path.Combine(outputPath, Path.GetFileName(FileName).Replace(".", "_"));
        if (!Directory.Exists(imageFilesFolder))
        {
            Directory.CreateDirectory(imageFilesFolder);
        }
        string imageFilesPath = Path.Combine(imageFilesFolder, "page-{0}.png");
        using (Viewer viewer = new Viewer(Path.Combine(storagePath, FileName)))
        {
            //Get document info
            ViewInfo info = viewer.GetViewInfo(ViewInfoOptions.ForPngView(false));
            pageCount = info.Pages.Count;
            //Set options and render document
            PngViewOptions options = new PngViewOptions(imageFilesPath);
            viewer.View(options);
        }
        return new JsonResult(pageCount);
    }
}

The method marked with the [HttpPost] tag, which indicates that it responds to HTTP POST requests, lies at the heart of this code. The method accepts a FileName parameter, which is the name of the uploaded file. The method returns an IActionResult, which allows for the return of many forms of replies, such as JSON, views, or redirects.

The code starts by creating a folder in which to save the created PNG images. The name of the folder is determined by the FileName option, with any dots in the filename replaced by underscores. If the folder does not already exist, the code uses the Directory to create it.The method CreateDirectory.

By combining the storage location and the FileName parameter, the using block is utilized to generate a Viewer object. This Viewer object is responsible for interacting with the document file.

For saving images, a PngViewOptions object is created and specified using the imageFilesPath pattern. The created choices are then passed to the View method of the viewer. This phase transforms the pages of the document as PNG images and saves them to the chosen folder.

The pageCount variable, which reflects the total number of pages in the document, is returned in the JSON response. The client or caller can utilize this JSON response to obtain this information.

Create an Index.cshtml file now.
In index.cshtml, we use an Ajax call.

@{
}


<script src="http://code.jquery.com/jquery-1.8.2.js"></script>
<script>
    function ViewDocument(file) {
        $("#loader").fadeIn();
        var data = { FileName: file };
        $.ajax({
            type: "POST",
            url: '/DocViewer/OnPost',
            data: data,
            dataType: "text"
        }).done(function (data) {
            var folderName = file.replace(".", "_");
            $("#content").empty();
            for (var i = 1; i <= data; i++) {
                $("#content").append("<img class='img-fluid' src='Content/" + folderName + "/page-" + i + ".png'/>");

            }
            $("#loader").fadeOut();
        })
    }
</script>
<script type="text/javascript">
    $(window).load(function () {
        $("#loader").fadeOut(1000);
    });
</script>
<div class="container">
    <div class="row">
        <div class="col-md-3">
            <div class="sidenav bg-light p-3">
                <div id="loader"></div>
                <h2 class="ps-3">Files</h2>
                @if (ViewBag.lstFiles != null)
                {
                    @foreach (string file in ViewBag.lstFiles)
                    {
                        <a href="#" onclick="ViewDocument('@file')" class="d-block">@file</a>
                    }
                }
            </div>
        </div>
        <div class="col-md-9">
            <h2>Preview</h2>
            <div id="content" class="border p-3"></div>
        </div>
    </div>
</div>

Output:
Image preview

Document file preview

GroupDocs.Viewer is a software development tool that offers APIs and libraries for viewing and visualizing different sorts of documents and files within applications. It enables developers to incorporate document viewing features into their apps without requiring users to install the native applications that generated those documents. The application supports a variety of document formats, including PDF, Microsoft Office (Word, Excel, PowerPoint), pictures, AutoCAD files, and others.

The current version of Microsoft's popular cross-platform programming framework is.NET 7. Minimal APIs, a new technique to construct lightweight, quick, and simple APIs with just a few lines of code, is one of the new features introduced in.NET 7. In this post, we'll look at how to use Minimal APIs in.NET 7, as well as how to add MapGroup() to a static class.

What exactly are Minimal APIs?
Minimal APIs are a new type of API introduced in.NET 7, allowing developers to construct APIs with minimal overhead and optimal efficiency. They are lightweight and simple to use, with an emphasis on simplicity and ease of development.How to create a Minimal API in .NET 7?

Creating a Minimal API in .NET 7 is simple. Here’s an example of how to create a Minimal API that returns “Hello World!” when you make a GET request to the root URL:
var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();
app.MapGet("/", () => "Hello World!");
app.Run();

In this example, we’ve used the WebApplication class to create a new Minimal API. We've then used the MapGet() method to map a GET request to the root URL ("/") and return "Hello World!".
Adding MapGroup() to a static class

MapGroup() allows you to group similar endpoints and apply shared middleware or configuration to them. To add MapGroup() to a static class, follow these steps:

1. Create a static class for your endpoints
public static class MyEndpoints
{
    public static void MapGroup(this IEndpointRouteBuilder endpoints)
    {
        endpoints.MapGet("/", Get).WithName("Get").WithOpenApi();

        endpoints.MapGet("/api/customers", GetCustomers).WithName("Customers").WithOpenApi();

        // Add more endpoints here
    }

    private static IResult Get()
    {
        return Results.Ok("Hello World!");
    }

    private static IResult GetCustomers()
    {
        return Results.Ok("List of customers");
    }
}

2. Add a MapGroup() call your endpoint configuration in the Startup class, and configure OpenAPI and Swagger services.
var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();
app.MapGroup();
app.Run();

In this example, we’ve added a call to MapGroup() and passed in an empty string as the group prefix and the MapGroup() method from our MyEndpoints static class.

Now, all the endpoints defined in MyEndpoints the class will be grouped under the specified prefix, which in this case, is an empty string. You can add a different prefix to group endpoints together and use the same prefix in your middleware or configuration for all endpoints in the group.

With MapGroup(), you can create modular and organized APIs with shared middleware and configuration for groups of endpoints.

Minimal APIs in.NET 7 make it simple to write lightweight, quick APIs with only a few lines of code. You can group comparable endpoints and apply shared middleware or configuration to them by adding MapGroup() to a static class. You can use these characteristics to construct simple and organized APIs that are straightforward to design and maintain.