In ASP.NET Core, a middleware component is a class that implements the IMiddleware interface or is a class that has a method named Invoke or InvokeAsync. To create a custom middleware component, you can create a new class and implement the InvokeAsync method. Here is an example of a custom middleware component that logs the request and response information:
public class RequestResponseLoggingMiddleware
{
private readonly RequestDelegate _next;
public RequestResponseLoggingMiddleware(RequestDelegate next)
{
_next = next;
}
public async Task InvokeAsync(HttpContext context)
{
// Log the request information
var request = context.Request;
Console.WriteLine($"{request.Method} {request.Path}");
foreach (var header in request.Headers)
{
Console.WriteLine($"{header.Key}: {header.Value}");
}
// Call the next middleware component
await _next(context);
// Log the response information
var response = context.Response;
Console.WriteLine($"{response.StatusCode}");
foreach (var header in response.Headers)
{
Console.WriteLine($"{header.Key}: {header.Value}");
}
}
}
To use this middleware component in your application, you need to add it to the Startup.cs Configure method, this can be done by using the UseMiddleware<T> extension method:
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
//...
app.UseMiddleware<RequestResponseLoggingMiddleware>();
//...
}
The order in which the middleware components are added to the IApplicationBuilder is important, the order that you add the middleware to the pipeline determines the order in which it is executed. Keep in mind that if you want your middleware component to perform some operation before or after other middleware components, you should add it accordingly in the pipeline.
Alternatively you can use the app.Use method as well, it's similar to UseMiddleware but it can be used for any type of middleware, not just classes that implement IMiddleware interface.
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