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.

In ASP.NET Core WebAPI, action injection refers to the process of injecting services directly into a controller's action methods. It enables you to get the services needed for a specific action method without having to inject them into the controller's constructor.

Services are often injected into a controller's constructor and are available for use throughout all action methods inside that controller in traditional dependency injection (DI). However, there may be times when you simply require a service within a specific action method. In such cases, action injection can be used to directly inject the required service into the method's argument.

In ASP.NET Core, the attribute '[FromServices]' is used to inject services straight into action methods of your controllers.

The [FromServices] attribute for action injection has been available since the initial release of ASP.NET Core, which is ASP.NET Core 1.0. It has been a part of the framework since its inception and is used to inject services directly into action methods within controllers.

Here is a way to employ the [FromServices] attribute within an ASP.NET Core WebAPI controller:

The tools which I have leveraged for this tutorial.
    VS 2022 Community Edition
    .NET 6.0
    Web API
Define a service interface and its implementation:
public interface IMyService
{
    string GetServiceInfo();
}

public class MyService : IMyService
{
    public string GetServiceInfo()
    {
        return "Example on Action Injection";
    }
}

Configure the service in your Program.cs:
builder.Services.AddTransient<IMyService, MyService>();

Use [FromServices] attribute in your controller action method:
namespace ActionInjection.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class MyController : ControllerBase
    {
        [HttpGet("info")]
        public IActionResult GetInfo([FromServices] IMyService myService)
        {
            var info = myService.GetServiceInfo();
            return Ok(info);
        }
    }
}

In this example, the GetServiceInfo action method uses [FromServices] attribute to directly inject the IMyService instance into the method parameter. ASP.NET Core will automatically resolve the service and provide it to the action method.

It's important to recognize that while leveraging [FromServices] can be advantageous under specific circumstances, the preferred approach for enhanced maintainability and testability—especially when a service is required across multiple action methods—is to opt for constructor injection (the constructor of the [Controller]).

FluentValidation is a very popular .NET library for building strongly-typed validation rules. It helps us use validation in a very easy manner. It is a small validation library that uses a fluent interface and lambda expressions for building validation rules.

What is FluentValidation in ASP.NET Core?
Data Validation is essential for any Application. When it comes to Validating Models, developers usually use Data Annotations. There are a few issues with the Data Annotations approach:

• Validation rules are tightly coupled with Entities.
• Add complexity to Entities/DTOs.
• Difficult to make dynamic and conditional validations.
• Difficult to extend and scale.

FluentValidation is a replacement for the existing validation attributes (Data Annotations). It can turn up the validation game to a new level and gives total control. It separates the validation rules and/or logic from the Entity/DTO classes.

It is an open-source library that helps you make validations clean, easy to create, and maintain. It also works on external models that you don’t have access to. It makes the model classes clean and readable.

Configure Fluent Validation in ASP.NET Core
1. NuGet: To use FluentValidation, you need to install below NuGet packages.
Install-Package FluentValidation.AspNetCore
Install-Package FluentValidation.DependencyInjectionExtensions

2. Configuration: Automatic registration of validators is possible. You can make use of FluentValidation.DependencyInjectionExtensions package, which can be used to automatically find all the validators in a specific assembly using an extension method.
using FluantValidationDemoApp.Data;
using FluentValidation.AspNetCore;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using System.Configuration;
using System.Reflection;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllers();

builder.Services.AddDbContext<ApplicationDBContext>(options =>
{
options.UseSqlite(builder.Configuration.GetConnectionString("DefaultConnection"));
});

builder.Services.AddControllers()
        .AddFluentValidation(v =>
        {
            v.ImplicitlyValidateChildProperties = true;
            v.ImplicitlyValidateRootCollectionElements = true;
            v.RegisterValidatorsFromAssembly(Assembly.GetExecutingAssembly());
        });

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.UseAuthorization();
app.MapControllers();
app.Run();

This adds FluentValidation to the pipeline for Controllers.

Validator Implementation
To define a set of validation rules for a particular object, you will need to create a class that inherits from AbstractValidator<T>, where T is the type of class that you wish to validate.

The validation rules themselves should be defined in the validator class’s constructor. To specify a validation rule for a particular property, call the RuleFor method, passing a lambda expression that indicates the property that you wish to validate.
using FluantValidationDemoApp.DTOs;
using FluentValidation;

namespace FluantValidationDemoApp.Validations
{
public class CustomerValidator : AbstractValidator<CustomerDTO>
{
    public CustomerValidator()
    {
        RuleFor(x => x.Name).NotNull().NotEmpty();
        RuleFor(x => x.Name).Length(20, 250);
        RuleFor(x => x.PhoneNumber).NotEmpty().WithMessage("Please specify a phone number.");
        RuleFor(x => x.Age).InclusiveBetween(18, 60);

        // Complex Properties
        RuleFor(x => x.Address).InjectValidator();

        // Other way
        //RuleFor(x => x.Address).SetValidator(new AddressValidator());

        // Collections of Complex Types
        //RuleForEach(x => x.Addresses).SetValidator(new AddressValidator());
    }
}
}

using FluantValidationDemoApp.DTOs;
using FluentValidation;

namespace FluantValidationDemoApp.Validations
{
public class AddressValidator : AbstractValidator<AddressDTO>
{
    public AddressValidator()
    {
        RuleFor(x => x.State)
            .NotNull()
            .NotEmpty();

        RuleFor(x => x.Country)
            .NotEmpty()
            .WithMessage("Please specify a Country.");

        RuleFor(x => x.Postcode)
            .NotNull()
            .Must(BeAValidPostcode)
            .WithMessage("Please specify a valid postcode");
    }

    private bool BeAValidPostcode(string postcode)
    {
        return postcode.Length == 6;
    }
}
}

Code Explanation
You can use the RuleForEach method to apply the same rule to multiple items in a collection.
You can also combine RuleForEach with SetValidator when the collection is of another complex object.
RuleSets allow you to group validation rules together, which can be executed together as a group whilst ignoring other rules.
Including Rules: You can include rules from other validators, provided they validate the same type. This allows you to split rules across multiple classes and compose them together.
Validators can be used with any dependency injection library. To inject a validator for a specific model, you should register the validator with the service provider as IValidator<T>. services.AddScoped<IValidator<Customer, CustomerValidator>();

namespace FluantValidationDemoApp.Entities
{
public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public int Age { get; set; }
    public string PhoneNumber { get; set; } = string.Empty;
    public bool IsAdult { get; set; }
    public Address? Address { get; set; }
}
}

namespace FluantValidationDemoApp.Entities
{
public class Address
{
    public int Id { get; set; }
    public string Line1 { get; set; } = string.Empty;
    public string Line2 { get; set; } = string.Empty;
    public string Town { get; set; } = string.Empty;
    public string Postcode { get; set; } = string.Empty;
    public string Country { get; set; } = string.Empty;
    public string State { get; set; } = string.Empty;
}
}

Usage: You don’t need to explicitly check the ModelState in controllers to see if the input is valid. The FluentValidation ASP.NET middleware will automatically find our validator, and if validation fails, it will prepare the ModelState, and our action will return a 400 response.
using FluantValidationDemoApp.Data;
using FluantValidationDemoApp.DTOs;
using FluantValidationDemoApp.Validations;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;

namespace FluantValidationDemoApp.Controllers
{
[Route("api/[controller]")]
[ApiController]
public class CustomerController : ControllerBase
{
    private readonly ApplicationDBContext _applicationDBContext;

    public CustomerController(ApplicationDBContext applicationDBContext)
    {
        _applicationDBContext = applicationDBContext;
    }

    [HttpPost("AddNewCustomer", Order = 0)]
    public IActionResult Add(CustomerDTO customer)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        _applicationDBContext.Add(customer);
        _applicationDBContext.SaveChanges();

        return Ok();
    }

    [HttpPost("UpdateNewCustomer", Order = 1)]
    public IActionResult Update(CustomerDTO customer)
    {
        CustomerValidator validator = new CustomerValidator();
        var validationResult = validator.Validate(customer);

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

        _applicationDBContext.Update(customer);
        _applicationDBContext.SaveChanges();

        return Ok();
    }
}
}

You can also explicitly validate the models anywhere. The Validate method returns a ValidationResult object. This contains two properties.

IsValid: a boolean that says whether the validation succeeded.
Errors: a collection of ValidationFailure objects containing details about any validation failures.

FluentValidation Features and Benefits

• Built-in Validators: ships with several built-in validators like Regular Expression, Email, Credit Card, and many more.
• Custom Validators: There are several ways to create a custom, reusable validator.
• Localization: provides translations for the default validation messages in several languages.
• Test Extensions: provides some extensions that can aid with testing your validator classes.
• Asynchronous Validation: you can define asynchronous rules, for example, when working with an external API.
• Transforming Values: you can apply a transformation to a property value prior to validation being performed against it.

In .NET Core, there are problems such as the bad complexity of web programming and the vagueness of coding in the controller, and the destruction of the web programming structure on the server side. Also, one of the negative points of .NET Core is the lack of support for aspx files. An executable physical file (aspx) in the root makes your program more structured.

Introducing Code-Behind
This style is completely based on MVC, and in the near future, we will expand it in such a way that there is no need for coding the view part, such as for, foreach, and while loops.

Write code with Code-Behind
You can add aspx files in the wwwroot directory and its subdirectories.

An example of an aspx file based on Code-Behind.
<%@ Page Controller="YourProjectName.wwwroot.DefaultController" Model="YourProjectName.wwwroot.DefaultModel" %><!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title><%=model.PageTitle%></title>
</head>
<body>
    <%=model.BodyValue%>
</body>
</html>

An example of a controller class that is based on Code-Behind.
using CodeBehind;

namespace YourProjectName.wwwroot
{
    public partial class DefaultController : CodeBehindController
    {
        public DefaultModel model = new DefaultModel();
        public void PageLoad(HttpContext context)
        {
            model.PageTitle = "My Title";
            model.BodyValue = "HTML Body";
            View(model);
        }
    }
}

An example of a model class that is based on Code-Behind.
using CodeBehind;

namespace YourProjectName.wwwroot
{
    public partial class DefaultModel : CodeBehindModel
    {
        public string PageTitle { get; set; }
        public string BodyValue { get; set; }
    }
}

Program file and additional Code-Behind items.
using CodeBehind;
using SetCodeBehind;

var builder = WebApplication.CreateBuilder(args);

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
    // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
    app.UseHsts();
}

+ CodeBehindCompiler.Initialization();

app.Run(async context =>
{
+    CodeBehindExecute execute = new CodeBehindExecute();
+    await context.Response.WriteAsync(execute.Run(context));
});

app.UseHttpsRedirection();
app.UseStaticFiles();

app.UseRouting();

app.Run();

In the Program.cs class codes above, the three values marked with the + character must be added.

We show the codes separately for you.
CodeBehindCompiler.Initialization();

CodeBehindExecute execute = new CodeBehindExecute();
await context.Response.WriteAsync(execute.Run(context));

You can use the Write method in the model and controller classes; the Write method adds a string value to the ResponseText attribute; you can also change the values of the ResponseText attribute by accessing them directly.

In the controller class, there is an attribute named IgnoreViewAndModel attribute, and if you activate the IgnoreViewAndModel attribute, it will ignore the values of model and view, and you will only see a blank page; this feature allows you to display the values you need to the user and avoid multiple redirects and transfers.

To receive the information sent through the form, you can follow the instructions below.

public DefaultModel model = new DefaultModel();
public void PageLoad(HttpContext context)
{
    if (!string.IsNullOrEmpty(context.Request.Form["btn_Add"]))
        btn_Add_Click();

    View(model);
}

private void btn_Add_Click()
{
    model.PageTitle = "btn_Add Button Clicked";
}

Note. After running the program and compiling the aspx pages by Code-Behind, your program will no longer refer to any aspx files. If the scale of the program you are building is high or you need to act dynamically, using Code-Behind will definitely give you more freedom. If the scale of the program is low, using Code-Behind will simplify your program, and you will generate faster and more understandable code.

The following example shows the power of Code-Behind

aspx page
<%@ Page Controller="YourProjectName.wwwroot.DefaultController" Model="YourProjectName.wwwroot.DefaultModel" %><!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title><%=model.PageTitle%></title>
</head>
<body>
    <%=model.LeftMenuValue%>
    <div class="main_content">
        <%=model.MainContentValue%>
    </div>
    <%=model.RightMenuValue%>
</body>
</html>

Controller class
using CodeBehind;

namespace YourProjectName.wwwroot
{
    public partial class DefaultController : CodeBehindController
    {
        public DefaultModel model = new DefaultModel();

        public void PageLoad(HttpContext context)
        {
            model.PageTitle = "My Title";
            CodeBehindExecute execute = new CodeBehindExecute();

            // Add Left Menu Page
            context.Request.Path = "/menu/left.aspx";
            model.LeftMenuValue = execute.Run(context);

            // Add Right Menu Page
            context.Request.Path = "/menu/right.aspx";
            model.RightMenuValue = execute.Run(context);

            // Add Main Content Page
            context.Request.Path = "/pages/main.aspx";
            model.MainContentValue = execute.Run(context);

            View(model);
        }
    }
}

Each of the pages is left.aspx, right.aspx, and main.aspx can also call several other aspx files; these calls can definitely be dynamic, and an add-on can be executed that the kernel programmers don't even know about.

Enjoy Code-Behind, but be careful not to loop the program! (Don't call pages that call the current page).
What power does Code-Behind give you while running the program?

Accessing hypertext contents of pages and replacing some values before calling in other pages.

Microsoft usually ties your hands, so you cannot create a dynamic system.

By using the default architecture of Microsoft's ASP.NET Core, you will face some very big challenges. Creating a system with the ability to support plugins that both provides security and does not loop, and can call other pages on your pages is very challenging.

Suppose you have created an application using the default ASP.NET Core cshtml that has a main page that includes a right menu and a left menu. As shown in the code above, can you change the values of these menus to Fill the dynamic form with cshtml pages and replace the values obtained from the pages? It is definitely possible, but it is difficult.

Code-Behind will not even refer to the physical aspx file to call the aspx pages and will only call a method.

How do you manage events in ASP.NET Core?
For example, a route from your program requires several methods to be executed, and these methods do not exist in the core of your program! This work can be blinded with the default cshtml of .NET, but it is difficult.

For example, we should have an event before the request to the search page and not allow the user to do more than 2 searches per minute. Using Code-Behind, we only need to check an aspx page, then reject or allow the search request.

In many web applications, there arises a need to download multiple files as a single zip archive. This scenario is common when dealing with document management systems, exporting data, or providing bulk downloads. In this article, we will explore how to enable users to download files in a zip format from a .NET Core Web API.

Step 1. Setting up the .NET Core Web API project
Open Visual Studio and create a new .NET Core Web API project.
Configure the project as per your requirements, including selecting a target framework and naming the project.

Step 2. Adding Required NuGet Packages
Right-click on the project in the Solution Explorer and select "Manage NuGet Packages."
Search for and install the "System.IO.Compression" and "System.IO.Compression.FileSystem" packages. These packages provide the necessary classes to work with ZIP files.

Step 3. Creating the File Download Endpoint
Create a new controller (or you can use an existing one also) that will handle the file download in zip format. In this example, we'll create a simple controller named FileController.

Add a new action method with an appropriate route to handle the file download.

Code Example
#nullable disable

using Microsoft.AspNetCore.Mvc;
using System.IO.Compression;

namespace ZipDownload.Controllers {
[ApiController]
[Route("api/files")]
public class FilesController: ControllerBase {
private readonly IWebHostEnvironment _hostEnvironment;

public FilesController(IWebHostEnvironment hostEnvironment) {
  _hostEnvironment = hostEnvironment;
}

[HttpGet]
[Route("download-zip")]
public IActionResult DownloadFiles() {
  try {
    var folderPath = Path.Combine(_hostEnvironment.ContentRootPath, "FilesToDownload");

    // Ensure the folder exists
    if (!Directory.Exists(folderPath))
      return NotFound("Folder not found.");

    // Get a list of files in the folder
    var files = Directory.GetFiles(folderPath);

    if (files.Length == 0)
      return NotFound("No files found to download.");

    // Create a temporary memory stream to hold the zip archive
    using(var memoryStream = new MemoryStream()) {
      // Create a new zip archive
      using(var zipArchive = new ZipArchive(memoryStream, ZipArchiveMode.Create, true)) {
        foreach(var file in files) {
          var fileInfo = new FileInfo(file);

          // Create a new entry in the zip archive for each file
          var entry = zipArchive.CreateEntry(fileInfo.Name);

          // Write the file contents into the entry
          using(var entryStream = entry.Open())
          using(var fileStream = new FileStream(file, FileMode.Open, FileAccess.Read)) {
            fileStream.CopyTo(entryStream);
          }
        }
      }

      memoryStream.Seek(0, SeekOrigin.Begin);

      // Return the zip file as a byte array
      return File(memoryStream.ToArray(), "application/zip", "files.zip");
    }
  } catch (Exception ex) {
    return StatusCode(500, $ "An error occurred: {ex.Message}");
  }
}
}
}

In the above code, the IWebHostEnvironment is injected into the constructor via dependency injection. It provides information about the web hosting environment, such as the content root path.

 Inside the DownloadFiles method, the first step is to construct the path to the folder containing the files to be downloaded. It combines the content root path obtained from _hostEnvironment.ContentRootPath with the folder name "FilesToDownload"

It then checks if the folder exists. If the folder does not exist, it returns a 404 Not Found response with a corresponding error message. Next, it retrieves a list of files present in the folder using Directory.GetFiles(folderPath). If there are no files in the folder, it returns a 404 Not Found response with an appropriate message.

A temporary MemoryStream is created to hold the zip archive that will be generated. Within the using statement, a new ZipArchive is created using the MemoryStream and the ZipArchiveMode.Create mode.

The code then iterates over each file in the folder and performs the following steps:

• Retrieves file information using FileInfo.
• Creates a new entry in the zip archive with the file name using the zip archive.CreateEntry(fileInfo.Name).
• Opens the entry stream and the file stream and copies the file contents into the entry using fileStream.CopyTo(entryStream).
• After all the files are added to the zip archive, the MemoryStream is rewound to the beginning using memoryStream.Seek(0, SeekOrigin.Begin).
• Finally, the zip archive is returned as a downloadable response by using the File method of the base controller class. It takes the byte array representation of the zip archive (memoryStream.ToArray()), the MIME type of the zip file ("application/zip"), and the desired file name ("files.zip") as parameters.

In case any exception occurs during the process, it catches the exception, and a 500 Internal Server Error response is returned with the corresponding error message.

Step 4. Testing the File Download Endpoint

• Run the Web API project and navigate to the download endpoint URL in a web browser or use a tool like Postman.
• Upon accessing the endpoint, the browser or tool should prompt the user to save the ZIP file.
• After downloading and extracting the ZIP file, the user will find all the requested files within the folder structure specified during creation.

In this article, we explored how to enable file downloads in ZIP format using a .NET Core Web API. By leveraging the System.IO.Compression namespace, we were able to compress multiple files into a single ZIP file and return it to the client. This approach offers a convenient way to bundle and deliver multiple files efficiently, improving the user experience when downloading content from a web application.

The Entity Framework (EF) Core is a lightweight, extendable, open-source, cross-platform version of the well-known Entity Framework data access technology. We'll look at the Code First technique in EF Core using a.NET 7 API in this article. This process begins with the definition of your model classes; EF Core then generates the database and its structure based on these models.

Why do we require EF Core?
Microsoft's EF Core is an open-source lightweight ORM that provides a mechanism to connect with relational databases using programming concepts. Here are some of the reasons why it is advantageous.

• Object-Relational Mapping: EF Core connects relational databases to object-oriented programming. It lowers the amount of boilerplate code required to convert database tables and columns into object properties. This is handled automatically by EF Core.
• Language Integrated Query (LINQ): LINQ is a strong querying language included with.NET. It enables developers to write database queries in C# syntax. LINQ converts our C# queries into efficient database queries.
• Testability is promoted by the design of EF Core, which allows developers to fake or alter the database context during unit testing. This allows developers to build isolated tests that do not rely on a physical database, making testing more efficient and reliable.

After project creation, we will have a structure like this.

Next, we will install the required nuget packages.

Install the following packages,

    Microsoft.EntityFrameworkCore
    Microsoft.EntityFrameworkCore.Design
    Microsoft.EntityFrameworkCore.SqlServer

Now we will create a folder called 'Models' in the solution, and inside it, we will add another folder called Entities which will have entity classes from which our database will be created.

We will create a class "Department.cs" with the following properties.
public class Department
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
    public bool IsActive { get; set; }
    public DateTime CreatedDate { get; set; }
    public DateTime UpdatedDate { get; set; }
}

Now we will create a class called "Employee.cs".
public class Employee
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public int DepartmentId { get; set; }

    public bool IsActive { get; set; }
    public DateTime CreatedDate { get; set; }
    public DateTime UpdatedDate { get; set; }
}

Now we will create an "EmployeeDbContext.cs".
public class EmployeeDbContext : DbContext
{
    public EmployeeDbContext(DbContextOptions<EmployeeDbContext> options) : base(options)
    {
    }

    public DbSet<Department> Departments { get; set; }
    public DbSet<Employee> Employees { get; set; }
}

As we can see, this EmployeeDbContext class extends from the DbContext class that comes in the "Microsoft.EntityFrameworkCore" framework, and then we have the DbSets for the Departments and Employees as per the entities we created.

Now we will configure the DB context in the "Program.cs".

We will add the following code.
builder.Services.AddDbContext<EmployeeDbContext>(options =>
{
    options.UseSqlServer("Server=RAVI;Database=EFCoreCodeFirstDB;Trusted_Connection=True;MultipleActiveResultSets=true;TrustServerCertificate=True;");
});

After that, we will run the migrations commands that will help us maintain the DB state.

Run the following command in the solution directory.

“dotnet ef migrations add InitialCreate”.

After running it, the output will look something like this.

In the solution explorer, you will see the following folder.

Note. If the above command throws the error, please run the following command first.
“dotnet tool install --global dotnet-ef”

After this, we will run the following command.
“dotnet ef database update”

You should see the following output.

After this, you can see your SqlServer to see that your database has been created along with your tables.

Now we will add a controller called "DepartmentController.cs".
[Route("api/[controller]")]
[ApiController]
public class DepartmentController: ControllerBase {
  private readonly EmployeeDbContext _dbContext;
  public DepartmentController(EmployeeDbContext dbContext) {
    _dbContext = dbContext;
  }

  [HttpGet]
  public IActionResult Get() {
    var departments = _dbContext.Departments.ToList();
    return Ok(departments);
  }

  [HttpPost]
  public IActionResult Post([FromBody] Department department) {
    _dbContext.Departments.Add(department);
    _dbContext.SaveChanges();
    return Ok();
  }

  [HttpPut]
  public IActionResult Put([FromBody] Department department) {
    var dept = _dbContext.Departments.FirstOrDefault(d => d.Id == department.Id);
    if (dept == null)
      return NotFound();

    dept.Name = department.Name;
    dept.Description = department.Description;
    dept.UpdatedDate = DateTime.Now;
    _dbContext.SaveChanges();
    return Ok(dept);
  }
}

In our DepartmentController.cs, we have three REST endpoints; one is HttpGet which will get us the list of all departments. The second endpoint is HTTP POST which will save the departments in the DB, and the last one is HTTPPUT which will update the department in the DB.

Similarly, we will have an employee controller as well, which will save, update and get employees.
[Route("api/[controller]")]
[ApiController]
public class EmployeeController: ControllerBase {
  private readonly EmployeeDbContext _dbContext;
  public EmployeeController(EmployeeDbContext dbContext) {
    _dbContext = dbContext;
  }

  [HttpGet]
  public IActionResult Get() {
    var employees = _dbContext.Employees.ToList();
    return Ok(employees);
  }

  [HttpPost]
  public IActionResult Add([FromBody] Employee employee) {
    _dbContext.Employees.Add(employee);
    _dbContext.SaveChanges();
    return Ok();
  }

  [HttpPut]
  public IActionResult Update([FromBody] Employee employee) {
    var emp = _dbContext.Employees.FirstOrDefault(d => d.Id == employee.Id);
    if (emp == null)
      return NotFound();

    emp.FirstName = employee.FirstName;
    emp.LastName = employee.LastName;
    emp.DepartmentId = employee.DepartmentId;
    emp.UpdatedDate = DateTime.Now;
    _dbContext.SaveChanges();
    return Ok(emp);
  }
}

Now let's run our API, and then we will hit the POST endpoint of the department's controller.

Now we will try to get all the departments by hitting the Get endpoint of departments.

Now we will create a new employee using the Post endpoint of the employee controller.

Now we will hit the Get endpoint of the employee controller.

Now we can verify the same values from the database as well.

As we can verify, our values are stored in the database as well.
We have seen how to create a .NET 7 API and use EF Core to interact with the relational database to store and get the data.

In this article, we will be sending push notifications to Android devices via C# Dot Net/.Net. Using Firebase Cloud Messaging API HTTP V1.

This article will guide using of FCM HTTP V1 over Legacy FCM API.

Legacy FCM API :
https://fcm.googleapis.com/fcm/send

HTTP
Latest FCM Http V1:
https://fcm.googleapis.com/v1/projects/myproject-b5ae1/messages:send

HTTP
The latest FCM Http V1 provides better security, Support for the new Client Platform version.
Section 1. Create/ Login in Firebase Console Account.
URL: https://console.firebase.google.com/

After creating of account/Login, Click on Add Project.

Section 2. Add Firebase to your Android project
Section 3. Go to Project Settings

Section 4. Enable FCM HTTP V1

Section 5. Create a .Net Web API project; write this code to generate a Bearer token for calling FCM HTTP V1 API.

Code
using System.IO;
using Google.Apis.Auth.OAuth2;
using System.Net.Http.Headers;
using System.Text;
using System.Web;
using System.Web.Configuration;
using System.Net.Http;
using System.Web.Http;

//----------Generating Bearer token for FCM---------------

string fileName = System.Web.Hosting.HostingEnvironment.MapPath("~/***-approval-firebase-adminsdk-gui00-761039f087.json"); //Download from Firebase Console ServiceAccount

string scopes = "https://www.googleapis.com/auth/firebase.messaging";
var bearertoken = ""; // Bearer Token in this variable

using(var stream = new FileStream(fileName, FileMode.Open, FileAccess.Read)) {
  bearertoken = GoogleCredential
    .FromStream(stream) // Loads key file
    .CreateScoped(scopes) // Gathers scopes requested
    .UnderlyingCredential // Gets the credentials
    .GetAccessTokenForRequestAsync().Result; // Gets the Access Token
}

Section 6. Follow this Step to Download the Json file from the Firebase Console Account (Project Settings -> Service Account -> Generate New Private Key) & Place the Json File in your Project directory.

Section 7. Place the downloaded JSON File in your .net Project directory.

Section 8. Install Google.Api.Auth from Nuget Package Manager

Section 9. Use the Authorization token generated above via c# code to call FCM HTTP V1 API; get the FCM Token of Android from an Android device. Test using Postman; a push notification will be sent to the Android device.

Section 10. On successful completion of the above steps, Implement Further, Create this Model Classes for storing Request & Response data.

Section 11. Call the FCM HTTP V1 API using the Authorization token generated & get the FCM id / Token from the Android device.

Section 12. Entire Code
#region FCM Auth & Send Notification To Mobile //notify FCM Code
public class Data {

  public string body {
    get;
    set;
  }

  public string title {
    get;
    set;
  }

  public string key_1 {
    get;
    set;
  }

  public string key_2 {
    get;
    set;
  }

}

public class Message {

  public string token {
    get;
    set;
  }

  public Data data {
    get;
    set;
  }

  public Notification notification {
    get;
    set;
  }

}

public class Notification {

  public string title {
    get;
    set;
  }

  public string body {
    get;
    set;
  }

}

public class Root {

  public Message message {
    get;
    set;
  }

}

public void GenerateFCM_Auth_SendNotifcn()

{
  //----------Generating Bearer token for FCM---------------

  string fileName = System.Web.Hosting.HostingEnvironment.MapPath("~/***-approval-firebase-adminsdk-gui00-761039f087.json"); //Download from Firebase Console ServiceAccount

  string scopes = "https://www.googleapis.com/auth/firebase.messaging";
  var bearertoken = ""; // Bearer Token in this variable
  using(var stream = new FileStream(fileName, FileMode.Open, FileAccess.Read))

  {

    bearertoken = GoogleCredential
      .FromStream(stream) // Loads key file
      .CreateScoped(scopes) // Gathers scopes requested
      .UnderlyingCredential // Gets the credentials
      .GetAccessTokenForRequestAsync().Result; // Gets the Access Token

  }

  ///--------Calling FCM-----------------------------

  var clientHandler = new HttpClientHandler();
  var client = new HttpClient(clientHandler);

  client.BaseAddress = new Uri("https://fcm.googleapis.com/v1/projects/***-approval/messages:send"); // FCM HttpV1 API

  client.DefaultRequestHeaders.Accept.Clear();
  client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

  //client.DefaultRequestHeaders.Accept.Add("Authorization", "Bearer " + bearertoken);
  client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", bearertoken); // Authorization Token in this variable

  //---------------Assigning Of data To Model --------------

  Root rootObj = new Root();
  rootObj.message = new Message();

  rootObj.message.token = "cEM68BIdTomaE0R2dbaO:APA91bG8XfOjU_GSPNQYCrJ4wzE7VmMPEsyudwtE41VWKzJcoT2f3wbKsKCHwk5s078ZL31mM258-BzdZPRNXAlc_fyzCzj2txLQvQ3u7jggDPHjYIMlHRgspXT0CudfK"; //FCM Token id

  rootObj.message.data = new Data();
  rootObj.message.data.title = "Data Title";
  rootObj.message.data.body = "Data Body";
  rootObj.message.data.key_1 = "Sample Key";
  rootObj.message.data.key_2 = "Sample Key2";
  rootObj.message.notification = new Notification();
  rootObj.message.notification.title = "Notify Title";
  rootObj.message.notification.body = "Notify Body";

  //-------------Convert Model To JSON ----------------------

  var jsonObj = new JavaScriptSerializer().Serialize(rootObj);

  //------------------------Calling Of FCM Notify API-------------------

  var data = new StringContent(jsonObj, Encoding.UTF8, "application/json");
  data.Headers.ContentType = new MediaTypeHeaderValue("application/json");

  var response = client.PostAsync("https://fcm.googleapis.com/v1/projects/**-approval/messages:send", data).Result; // Calling The FCM httpv1 API

  //---------- Deserialize Json Response from API ----------------------------------

  var jsonResponse = response.Content.ReadAsStringAsync().Result;
  var responseObj = new JavaScriptSerializer().DeserializeObject(jsonResponse);

}

#endregion

In contemporary web applications, it is frequently necessary to upload files. Whether it involves uploading images, documents, or any other file format, ensuring a seamless user experience when dealing with uploads is crucial. This article will delve into the process of incorporating file upload functionality into an ASP.NET Core Web API.

Setting up the Project
To begin, we will set up a new ASP.NET Core Web API project. We'll also install the necessary NuGet packages required for file handling, such as
    Microsoft.EntityFrameworkCore.SqlServer
    Microsoft.EntityFrameworkCore
    Microsoft.EntityFrameworkCore.Tools

The tools which have been leveraged for this tutorial are.
    Visual Studio Community Edition 16.4.5
    .NET 6.0
    Entity Framework Core
    Web API

The entire source code can be downloaded from GitHub.

Creating the Model and Database Context
In this section, we'll define the model class representing the uploaded files and the corresponding database context for storing the file data. We'll use Entity Framework Core to interact with the database and store the file information as byte arrays.

Create a model class to represent the image entity. In this example, let's call it ImageEntity.cs:
public class ImageEntity
{
    [Key]
    public int Id { get; set; }

    public string FileName { get; set; }

    public byte[] Data { get; set; }
}

Then, create a database context class, AppDbContext.cs, that inherits from DbContext and includes a DbSet for the ImageEntity:
public class AppDbContext : DbContext
{
    public AppDbContext(DbContextOptions<AppDbContext> options)
        : base(options)
    {
    }

    public DbSet<ImageEntity> Images { get; set; }
}

Handling Multiple File Uploads in the Controller
In this segment, we will develop a controller action that receives an IFormFile object to manage file uploads. We will extract the file data and store it in the database utilizing the database context.

Create a controller, ImagesController.cs, with two actions: one for uploading the file and another for retrieving the file:
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;

namespace FileUploadsPOC.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class ImagesController : ControllerBase
    {
        private readonly AppDbContext _dbContext;


        public ImagesController(AppDbContext dbContext)
        {
            _dbContext = dbContext;

        }

        [HttpPost("upload")]
        public async Task<IActionResult> Upload(IFormFile file)
        {
            if (file == null || file.Length == 0)
                return BadRequest("No file uploaded.");

            var imageEntity = new ImageEntity
            {
                FileName = file.FileName
            };

            using (var memoryStream = new MemoryStream())
            {
                await file.CopyToAsync(memoryStream);
                imageEntity.Data = memoryStream.ToArray();
            }

            await _dbContext.Images.AddAsync(imageEntity);
            await _dbContext.SaveChangesAsync();

            return Ok(imageEntity.Id);
        }

        [HttpGet("download/{id}")]
        public async Task<IActionResult> Download(int id)
        {
            var imageEntity = await _dbContext.Images.FirstOrDefaultAsync(image => image.Id == id);

            if (imageEntity == null)
                return NotFound();

            var fileContentResult = new FileContentResult(imageEntity.Data, "application/octet-stream")
            {
                FileDownloadName = imageEntity.FileName
            };

            return fileContentResult;
        }
    }
}

Setup the configuration
Make sure to configure your database connection string in the appsettings.json file:
"ConnectionStrings": {
    "DefaultConnection": "Server=localhost;Database=FileUploadPOC;Trusted_Connection=SSPI;Encrypt=false;TrustServerCertificate=true"
  }

Configure your database connection and add the required services to Program.cs
builder.Services.AddDbContext<AppDbContext>(options =>
            options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));

Create the Database Migration and Update Database
Open the Package Manager Console and execute the below commands.

Add-Migration FileUpload (FileUpload is the name of the migration, you can provide any name at your convenience)

Once the build succeeds, execute the below command.
Update-database

Testing the Upload and Download Functionality
To ensure our file upload functionality works as expected, we'll test it using a tool like Postma. I will leave this to you.

Following the steps outlined in this blog post, you can easily enable this feature in your web applications. Happy coding!