ASP.NET Core - Middleware

ASP.NET Core - Middleware

Introduction ASP.NET Core middleware is a component-based approach to handling HTTP requests and responses in an ASP.NET Core application. Middleware sits between the web server and the application, allowing you to perform various tasks such as authentication, routing, logging, and more. This documentation provides an overview of middleware in ASP.NET Core and demonstrates how to use it effectively.

Middleware Pipeline In ASP.NET Core, the request processing pipeline consists of a series of middleware components. Each component handles a specific aspect of the request and passes it along to the next component in the pipeline. The pipeline is typically defined in the Configure method of the Startup class.

csharp
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    else
    {
        app.UseExceptionHandler("/Home/Error");
        app.UseHsts();
    }

    app.UseHttpsRedirection();
    app.UseStaticFiles();
    
    // Add your middleware components here
    
    app.UseRouting();
    app.UseAuthorization();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllerRoute(
            name: "default",
            pattern: "{controller=Home}/{action=Index}/{id?}");
    });
}

Creating Custom Middleware You can create custom middleware components to add functionality to your application. A middleware component is a class that implements the IMiddleware interface or has a method with the signature Task InvokeAsync(HttpContext context, RequestDelegate next). Here's an example of a custom middleware component that logs the request information:

csharp
public class RequestLoggerMiddleware : IMiddleware
{
    private readonly ILogger<RequestLoggerMiddleware> _logger;

    public RequestLoggerMiddleware(ILogger<RequestLoggerMiddleware> logger)
    {
        _logger = logger;
    }

    public async Task InvokeAsync(HttpContext context, RequestDelegate next)
    {
        _logger.LogInformation("Received request: {Method} {Path}", context.Request.Method, context.Request.Path);

        await next(context);
    }
}

Registering Custom Middleware To use custom middleware, you need to register it in the Configure method of the Startup class. You can use the UseMiddleware<T> method to register middleware components. Here's an example of registering the RequestLoggerMiddleware:

csharp
public void Configure(IApplicationBuilder app)
{
    // Other middleware components
    
    app.UseMiddleware<RequestLoggerMiddleware>();

    // Other middleware components
}

Ordering Middleware Components The order in which you register middleware components determines the order in which they are executed in the pipeline. You can change the order by moving the registration code within the Configure method. For example, if you want the RequestLoggerMiddleware to execute before the routing middleware, you can register it before calling app.UseRouting().

Conclusion Middleware in ASP.NET Core provides a flexible way to handle HTTP requests and responses. You can use built-in middleware components or create custom ones to add functionality to your application. Understanding the middleware pipeline and properly ordering the components allows you to control the request processing flow effectively.