Add Custom Middleware In ASP.Net Core 6 App

What is Middleware?

Middleware is software embedded in the app pipeline that processes requests and responses. ASP.NET Core provides a rich set of built-in middleware components, but in some scenarios, you may need to write custom middleware.

Let's see with a practical example

Learn how to create your own custom middleware and add it to your ASP.NET Core application's request pipeline.

A custom middleware component is like any other .NET class with an Invoke() method. However, the constructor needs her RequestDelegate type parameter to execute the following middlewares in order:

Visual Studio includes templates for creating standard middleware classes. To do this, right-click the project or folder where you want to create the middleware class and select Add -> New Item. This will open the Add New Item popup. In the top right search box, search for the word "middleware" as shown below.

Select the class and give it a name and then click on Add.

This will look as shown below. (Middleware class added with extension method)

// You may need to install the Microsoft.AspNetCore.Http.Abstractions package into your project
public class MyMiddleware {
    private readonly RequestDelegate _next;
    public MyMiddleware(RequestDelegate next) {
        _next = next;
    }
    public Task Invoke(HttpContext httpContext) {
        return _next(httpContext);
    }
}
// Extension method used to add the middleware to the HTTP request pipeline.
public static class MyMiddlewareExtensions {
    public static IApplicationBuilder UseMyMiddleware(this IApplicationBuilder builder) {
        return builder.UseMiddleware < MyMiddleware > ();
    }
}

As mentioned above, the Invoke() method is not asynchronous. So change it to asynchronous and write your custom logic before calling next();

//------------------------- Async Middleware :Rajesh Gami-----------------------
public class MyMiddleware {
    private readonly RequestDelegate _next;
    private readonly ILogger _logger;
    public MyMiddleware(RequestDelegate next, ILoggerFactory logFactory) {
        _next = next;
        _logger = logFactory.CreateLogger("MyMiddleware");
    }
    public async Task Invoke(HttpContext httpContext) {
        _logger.LogInformation("MyMiddleware executing..");
        await _next(httpContext); // calling next middleware
    }
}
// Extension method used to add the middleware to the HTTP request pipeline.
public static class MyMiddlewareExtensions {
    public static IApplicationBuilder UseMyMiddleware(this IApplicationBuilder builder) {
        return builder.UseMiddleware < MyMiddleware > ();
    }
}

Add Custom Middleware

Next, we need to add our custom middleware to the request pipeline using an extension method as shown below.

Add Middleware into Request Pipeline:

//************ Startup.cs *************
public void Configure(IApplicationBuilder app, IHostingEnvironment env) {
    app.UseMyMiddleware();
    app.Run(async (context) => {
        await context.Response.WriteAsync("Hello Rajesh Gami!");
    });
}

You can also add middleware using the IApplicationBuilder 's app.UseMiddleware() method.

Therefore, you can add custom middleware to your ASP.NET Core application.

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