In modern web development, making HTTP requests is a fundamental aspect of building robust and dynamic applications. In the .NET Core ecosystem, the HttpClient class has long been the go-to choice for sending HTTP requests. However, as applications grow in complexity, managing instances of HttpClient can become a challenge. This is where the HttpClientFactory in .NET Core comes to the rescue, providing a more efficient and scalable solution for handling HTTP requests.

HttpClient: What is it?
Developers can send and receive HTTP requests and responses by using the HttpClient class in the System.Net.Http namespace. Because of its portability and ability to establish and manage HTTP connections, it can be used in situations where several requests are sent to the same endpoint.

This is a simple example of sending a GET request using HttpClient.

using System;
using System.Net.Http;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        using (HttpClient client = new HttpClient())
        {
            string url = "https://api.example.com/data";
            HttpResponseMessage response = await client.GetAsync(url);

            if (response.IsSuccessStatusCode)
            {
                string result = await response.Content.ReadAsStringAsync();
                Console.WriteLine(result);
            }
        }
    }
}

Even if this method functions, it's not the most effective for handling several requests at once. It is typically not advised to create a new instance of HttpClient for each request as this can cause problems such as socket exhaustion.

HttpClientFactory: What is it?
The HttpClientFactory is part of the Microsoft.Extensions.In order to overcome the problems of manually managing HttpClient instances, the http package was established. It offers a more organized and scalable method for setting up, configuring, and administering HttpClient instances.

Principal Advantages of Using HttpClientFactory

• Lifetime Management: It manages the HttpClient instances' lifecycle, reusing existing connections to avoid problems like socket exhaustion.
• Configuration: HttpClientFactory makes it easier to manage many API endpoints with distinct settings by enabling you to configure HttpClient objects through named clients.
• Dependency Injection Integration: It makes injecting HttpClient objects into your services simple by integrating smoothly with the ASP.NET Core dependency injection framework.

HttpClientFactory use
Let's begin by going over how to use HttpClientFactory in a.NET Core application step-by-step.
1. Set up the required NuGet package.
dotnet add package Microsoft.Extensions.Http

2. Configure HttpClient in Startup.cs
services.AddHttpClient("MyApiClient", client =>
{
    client.BaseAddress = new Uri("https://api.example.com/");
    // Additional configuration options can be set here
});

3. Inject HttpClient into your service
public class MyService
{
    private readonly HttpClient _httpClient;

    public MyService(HttpClient httpClient)
    {
        _httpClient = httpClient;
    }

    // Use _httpClient to make requests
}

4. Use IHttpClientFactory for manual creation (optional)
If you need more control, you can inject IHttpClientFactory and create HttpClient instances manually.
public class MyService
{
    private readonly IHttpClientFactory _httpClientFactory;

    public MyService(IHttpClientFactory httpClientFactory)
    {
        _httpClientFactory = httpClientFactory;
    }

    public async Task MakeRequest()
    {
        HttpClient client = _httpClientFactory.CreateClient("MyApiClient");
        HttpResponseMessage response = await client.GetAsync("/data");
        // Handle the response
    }
}

In order to effectively use HttpClient and fully utilize HttpClientFactory, one must grasp HTTP requests in.NET Core. By implementing best practices, developers may create scalable and performant apps that communicate with external APIs with ease. Examples of these practices include controlling the lifetime of HttpClient objects and utilizing dependency injection. Developers may design dependable, high-performance solutions for managing HTTP requests in their.NET Core applications with the help of HttpClient and HttpClientFactory.

Overview of the Entity Framework
A strong and adaptable Object-Relational Mapping (ORM) framework that makes database interactions in.NET applications easier is called Entity Framework (EF). We'll explore several Entity Framework techniques in this extensive tutorial, with examples to help even.NET novices understand the ideas.

Entity Framework removes the requirement for developers to write raw SQL queries by enabling them to communicate with databases using.NET objects. It supports various strategies, each having benefits and applications of its own.

1. A database-first strategy
The Database-First method entails building the database first, then using it to generate the model.
Actions

• Build Database: Using SQL Server Management Studio or another database tool, design and build the database.
• Create Model: To create the model from the current database, use the Entity Data Model Wizard.
• Employ Created Classes For database activities, make use of the automatically produced classes.

// Auto-generated class representing a table in the database
public partial class Product
{
    public int ProductID { get; set; }
    public string ProductName { get; set; }
    // Other properties
}

// Usage in code
using (var context = new YourDbContext())
{
    var products = context.Products.ToList();
    // Perform operations on products
}

2. Code-First Approach
The Code-First method starts with the creation of the domain classes, from which the database is then generated.
Actions

• Establish domain classes that represent entities by using define classes.
• Establish Relationships: To establish relationships between entities, use Data Annotations or Fluent API.
• Create Database: Based on the model, create and update the database using migrations.

public class Product
{
    public int ProductID { get; set; }
    public string ProductName { get; set; }
    // Other properties
}

public class YourDbContext : DbContext
{
    public DbSet<Product> Products { get; set; }
    // Other DbSets

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        // Fluent API configuration for relationships
    }
}

3. Model-First Method
Using the Entity Data Model Designer, the Entity Data Model (EDM) is created, and the database is subsequently generated from it via the Model-First approach.
Actions

• To develop an Entity Data Model, use the Entity Data Model Designer.
• Generate Database: Select the Generate Database from Model option to generate the database from the EDM.

As an illustration
With Entity Data Model Designer, the model-first approach frequently incorporates visual design, which makes it less code-oriented.

4. Context of Databases and LINQ Queries
Whichever strategy is used, after the model is created developers use a database context to communicate with the database via LINQ queries.

using (var context = new YourDbContext())
{
    var products = from p in context.Products
                   where p.ProductName.Contains("Shoes")
                   select p;

    // Perform operations on products
}

Comprehending the various methodologies in Entity Framework enables.NET developers to select the most appropriate technique for their project needs. Entity Framework offers flexibility and abstraction for effective database interactions in.NET applications, regardless of your preference for building databases first, writing classes, or using visual modeling.

Have fun with coding!

To start a new ASP.NET Core Web API project, use the command line or Visual Studio.
dotnet new webapi -n WorkingwithSQLLiteinAsp.NETCoreWebAPI
cd WorkingwithSQLLiteinAsp.NETCoreWebAPI

Install SQLite NuGet Package
Install the SQLite NuGet package to enable SQLite support in your project.
dotnet add package Microsoft.EntityFrameworkCore.Sqlite

Now Create SQLite Database File in your Project
SQLLiteDatabase.db

Create Model
namespace WorkingwithSQLLiteinAsp.NETCoreWebAPI.Models
{
    // Models/TodoItem.cs
    public class TodoItem
    {
        public long Id { get; set; }
        public string Name { get; set; }
        public bool IsComplete { get; set; }
    }

}

Now Crete Application Database Context
using Microsoft.EntityFrameworkCore;
using WorkingwithSQLLiteinAsp.NETCoreWebAPI.Models;

namespace WorkingwithSQLLiteinAsp.NETCoreWebAPI.ApplicationDbContext
{
    public class AppDbContext : DbContext
    {
        public AppDbContext(DbContextOptions<AppDbContext> options) : base(options) { }

        public DbSet<TodoItem> TodoItems { get; set; }
    }
}

Add Connection string in AppSetting.JSON File
// appsettings.json
{
  "ConnectionStrings": {
    "DefaultConnection": "Data Source=SQLLiteDatabase.db"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*"
}

Register the Dependancy in Program.cs File
using Microsoft.EntityFrameworkCore;
using Microsoft.OpenApi.Models;
using WorkingwithSQLLiteinAsp.NETCoreWebAPI.ApplicationDbContext;

var builder = WebApplication.CreateBuilder(args);
var configuration = builder.Configuration;

// Add services to the container.
builder.Services.AddDbContext<AppDbContext>(options =>
        options.UseSqlite(configuration.GetConnectionString("DefaultConnection")));
builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v1", new OpenApiInfo { Title = "Working with SQLLite In Asp.net Core Web API", Version = "v1" });

});

var app = builder.Build();

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

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

Create and Apply Migrations
Run the following commands to create and apply migrations to create the SQLite database.
dotnet ef migrations add InitialCreate
dotnet ef database update

CRUD Operations
Implement CRUD operations in your controller.
// Controllers/TodoController.cs
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using WorkingwithSQLLiteinAsp.NETCoreWebAPI.ApplicationDbContext;
using WorkingwithSQLLiteinAsp.NETCoreWebAPI.Models;

[ApiController]
[Route("api/[controller]/[Action]")]
public class TodoController : ControllerBase
{
    private readonly AppDbContext _context;

    public TodoController(AppDbContext context)
    {
        _context = context;
    }

    // GET: api/Todo
    [HttpGet]
    public async Task<ActionResult<IEnumerable<TodoItem>>> GetTodoItems()
    {
        return await _context.TodoItems.ToListAsync();
    }

    // GET: api/Todo/5
    [HttpGet("{id}")]
    public async Task<ActionResult<TodoItem>> GetTodoItem(long id)
    {
        var todoItem = await _context.TodoItems.FindAsync(id);

        if(todoItem == null)
        {
            return NotFound();
        }

        return todoItem;
    }

    // POST: api/Todo
    [HttpPost]
    public async Task<ActionResult<TodoItem>> PostTodoItem(TodoItem todoItem)
    {
        _context.TodoItems.Add(todoItem);
        await _context.SaveChangesAsync();

        return CreatedAtAction(nameof(GetTodoItem), new { id = todoItem.Id }, todoItem);
    }

    // PUT: api/Todo/5
    [HttpPut("{id}")]
    public async Task<IActionResult> PutTodoItem(long id, TodoItem todoItem)
    {
        if(id != todoItem.Id)
        {
            return BadRequest();
        }

        _context.Entry(todoItem).State = EntityState.Modified;

        try
        {
            await _context.SaveChangesAsync();
        }
        catch(DbUpdateConcurrencyException)
        {
            if(!TodoItemExists(id))
            {
                return NotFound();
            }
            else
            {
                throw;
            }
        }

        return NoContent();
    }

    // DELETE: api/Todo/5
    [HttpDelete("{id}")]
    public async Task<IActionResult> DeleteTodoItem(long id)
    {
        var todoItem = await _context.TodoItems.FindAsync(id);
        if(todoItem == null)
        {
            return NotFound();
        }

        _context.TodoItems.Remove(todoItem);
        await _context.SaveChangesAsync();

        return NoContent();
    }

    private bool TodoItemExists(long id)
    {
        return _context.TodoItems.Any(e => e.Id == id);
    }
}

Output

Conclusion
SQLite is a relational database management system (RDBMS) that is self-contained, serverless, and requires no configuration. It is an embedded database engine that is lightweight, open-source, and runs directly on the client device, eliminating the need for a separate server process. Some of SQLite's key features are.

• Self-contained: It is simple to install and maintain because the whole database system is housed in a single library.
• Serverless: SQLite does not function as a separate server process, in contrast to conventional database management systems. Rather, it is incorporated straight into the program.
• Zero-configuration: Complex setup or administration are not necessary for SQLite. The database is a single, straightforward file that often has a.db extension; no server setup or upkeep is required.
• Cross-platform: SQLite is compatible with a number of operating systems and mobile platforms, including iOS and Android, as well as Windows, macOS, and Linux.
• Single-user: Because SQLite is optimized for single-user applications, embedded systems, mobile apps, and lightweight desktop programs can all benefit from its use.
• ACID-compliant: SQLite preserves the ACID (Atomicity, Consistency, Isolation, Durability) qualities, guaranteeing data reliability and integrity, even with its lightweight design.
• Dynamic typing: SQLite stores data using dynamic typing, which enables users to store several kinds of data in the same column.
• Broad language support: SQLite is adaptable to a variety of development contexts since it supports a wide range of programming languages, including C, C++, Java, Python, and.NET.

SQLite is often utilized in situations where a lightweight and integrated database solution is needed, such as mobile applications, desktop software, and embedded systems, because of its simplicity, portability, and ease of integration.

FluentValidation: What Is It?
An open-source validation toolkit for.NET called FluentValidation offers a fluid interface for creating and implementing validation rules. It makes validation logic easy to comprehend, write, and maintain by enabling developers to describe it succinctly and clearly.

.NET 8's FluentValidation
Installing the FluentValidation NuGet package is required in order to use FluentValidation in.NET 8. The following command can be used to accomplish this in the.NET CLI or Package Manager Console:

dotnet add package FluentValidation

Verifying a Basic User Model
Let's construct a straightforward example in which we wish to validate a User class. To make sure the user's email address is legitimate and their name is not empty, we will use FluentValidation.

using FluentValidation;

public class User
{
    public string Name { get; set; }
    public string Email { get; set; }
}

public class UserValidator : AbstractValidator<User>
{
    public UserValidator()
    {
        RuleFor(user => user.Name).NotEmpty().WithMessage("Name cannot be empty");
        RuleFor(user => user.Email).NotEmpty().EmailAddress().WithMessage("Invalid email address");
    }
}

In this instance:

• We provide properties for Name and Email in our User class definition.
• We construct a class called UserValidator, which is derived from AbstractValidator<User>.
• We define validation rules for the Name and Email properties inside the UserValidator constructor using the RuleFor method.

Applying FluentValidation to Your Software
Let's look at how we can utilize FluentValidation in our application now that we have our User class and matching validator:

class Program
{
    static void Main()
    {
        var user = new User { Name = "Mahesh Chand", Email = "[email protected]" };
        var validator = new UserValidator();

        var validationResult = validator.Validate(user);

        if (validationResult.IsValid)
        {
            Console.WriteLine("User is valid");
        }
        else
        {
            foreach (var error in validationResult.Errors)
            {
                Console.WriteLine($"Validation Error: {error.ErrorMessage}");
            }
        }
    }
}

In this instance:

• We construct an instance of the User class and set its properties.
• We instantiate a UserValidator object.
• By handing in the User instance, we invoke the Validate method on the validator.
• We verify the validity of the validation result. We print a success message if it is. If not, we repeat the mistakes and print them.

.NET 8's FluentValidation offers a tidy and expressive approach to handling validation in your applications. You can confidently design and run validation rules thanks to its fluid interface and simple syntax. Using FluentValidation makes it possible to isolate your validation logic apart from your business logic, as seen in our example, which makes your codebase easier to read and manage.

Cross-Origin Resource Sharing (CORS) is a vital security feature that controls how resources on a web page can be accessed by web applications from different domains. In an ASP.NET Core project, enabling CORS involves configuring the server to allow or restrict access to its resources from different origins. Here's a step-by-step guide on establishing CORS in your ASP.NET Core application.

Step 1. Set up the middleware for CORS

Installing the Microsoft.AspNetCore.Cors package is the first step. Using the NuGet Package Manager Console, you may accomplish this.

Install-Package Microsoft.AspNetCore.Cors

Alternatively, you can add it to your project's .csproj file:
<PackageReference Include="Microsoft.AspNetCore.Cors" Version="x.x.x" />

Replace x.x.x with the latest version available.

Step 2. Configure CORS in Startup.cs
Open your Startup.cs file and locate the ConfigureServices method. Add the CORS service by calling AddCors in the ConfigureServices method.
public void ConfigureServices(IServiceCollection services)
{
    // Other configurations

    services.AddCors(options =>
    {
        options.AddPolicy("AllowSpecificOrigin",
            builder =>
            {
                builder.WithOrigins("https://example.com")
                       .AllowAnyHeader()
                       .AllowAnyMethod();
            });
    });

    // Other configurations
}

In the code snippet above:

• The CORS services are added to the application's service container via AddCors.
• AddPolicy generates a specified CORS policy that identifies permitted origins, headers, and methods ("AllowSpecificOrigin" in this example).

To designate which domains are permitted to access your resources, modify WithOrigins. To accept requests from any origin, use a "*".

Step 3. Turn on the CORS middleware
Add the CORS middleware to Startup.cs's Configure function.

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // Other configurations

    app.UseCors("AllowSpecificOrigin");

    // Other configurations
}

This middleware must be added before other middleware that may handle requests, such as MVC or static file middleware.

Step 4: Verify Your CORS Setup
Once set up, make queries to your ASP.NET Core APIs from various origins to test the CORS settings. Make that the methods, headers, and permitted origins meet the needs of your application.

In summary
For secure communication between your application and clients from different domains, and to control access to your resources, you must implement CORS in your ASP.NET Core project. You can increase the security of your application while enabling critical cross-origin communication by defining CORS policies, which allow you to control which origins can access your APIs.

Always keep in mind to properly set your CORS policies based on the security requirements of your application, keeping in mind the possible hazards related to cross-origin requests.

One of the most frequent problems that developers encounter in the intricate and ever-changing process of software creation is the "class explosion." This happens when a software system has a lot of classes—often more than what was planned or organized in the first place. We will examine the reasons behind the class explosion, how it affects software systems, and management and mitigation techniques in this post.

Reasons for the Explosion of Classes
Excessively Fine-Grained Design: An excessively fine-grained design is one of the main reasons for class explosion. The number of classes can grow rapidly when every task or feature is included within a distinct class without a clear and obvious goal in mind.

class UserManager { }

Inadequate Abstraction: An excessive number of classes may result from improper abstraction. Class fragmentation occurs when developers are unable to recognize and produce meaningful abstractions, leading to an abundance of tiny, specialized classes.

class User { }
class UserValidationHelper { }
class UserPersistenceManager { }

Insufficient Planning: In some cases, inadequate upfront planning can contribute to class explosion. If the design lacks a clear structure and roadmap, developers might introduce new classes in a reactionary manner, leading to an unmanageable number of classes.

class FeatureAProcessor { }
class FeatureBProcessor { }
class FeatureCProcessor { }

The effects of the class explosion

• Complexity and Cognitive Load: The system's total complexity rises with the number of classes. The relationships and responsibilities of each class may be difficult for developers to understand, which will raise their cognitive load.
• Maintenance Challenges: Having a lot of classes may make maintenance difficult. It becomes more difficult to make modifications or add new features since developers have to work their way through a complex class hierarchy.
• Decreased Reusability: Decreased reusability may result from an excessive number of classes. It's possible that developers will have to start from scratch if they try to utilize tiny, specialized classes in other areas of the system.

Techniques to Control Class Explosion
Refactoring: Examine and reorganize the codebase on a regular basis to find and remove superfluous classes. Combine features into classes that are well-thought-out and integrated.

class UserManager { }

Abstraction and Encapsulation: Emphasize proper abstraction and encapsulation to ensure that classes have well-defined responsibilities. Avoid creating classes for every minor task and focus on creating meaningful, high-level abstractions.
    class User { }
    class UserManager { }

​​​Design Patterns: Utilize design patterns to manage class complexity. Patterns like the Singleton pattern, Factory pattern, and Strategy pattern can help organize and streamline class hierarchies.

class UserFactory { }

Modularization: Modularize the system into manageable modules or components. Divide the system into cohesive parts, each with a distinct responsibility, to prevent the proliferation of classes.
class AuthenticationModule { }

Guidelines and Code Reviews: Establish coding guidelines and conduct regular code reviews to ensure that the development team adheres to best practices. Enforce consistency in class design and encourage developers to think about the overall system architecture.

Example: Refactoring a Class Explosion
Consider a scenario where a class explosion has occurred in a system responsible for handling various geometric shapes:

class SquareValidator { }
class SquareCalculator { }
class CircleValidator { }
class CircleCalculator { }
class TriangleValidator { }
class TriangleCalculator { }

There are numerous classes as a result of this design's lack of abstraction. Let's rework this situation by adding an abstract and more unified design:

abstract class Shape { }
class Square extends Shape { }
class Circle extends Shape { }
class Triangle extends Shape { }

class ShapeValidator { }
class ShapeCalculator { }

We've added an abstract Shape class as part of this refactoring, which eliminates duplication and creates a more organized and manageable design.

In summary
Although class explosion is a typical problem in software design, it may be controlled and lessened with careful planning, frequent refactoring, and strict code standards. Developers can design systems that are not only scalable but also easier to understand and manage over time by placing a strong emphasis on appropriate abstraction, encapsulation, and modularization. Recall that a well-designed system prioritizes the classes' meaningful order and coherence over their quantity.