A Simple Web API Application that Echoes the Request for any URL

Download full source code.

There are times when playing with .NET that I want to make a simple HTTP request and get a response, this often happens to me when I’m trying to figure something out about HttpClient, HttpClientFactory, or Polly.

Of course, I can create a Web API application, and have it return some type. But then I probably want it to support the methods GET/PUT/POST/PATCH/DELETE, and even SEARCH (I like the SEARCH HTTP method).

Now it’s becoming a bit more work to program this up. And what if I want to make sure the correct headers are being sent and received? Now I need to process the incoming request and parse the headers.

Instead, I create a simple Web API application, and all it does is echo the request back in the response. A single endpoint or a single controller can handle all the HTTP methods, all URLs, and return as much as you want about the incoming request.

The Response

The first thing I need is a model to send the response. I’ll call it EchoResponse, I’ve included the properties I’m interested in -

public class EchoResponse
{
   public string Body { get; set; }
   public IHeaderDictionary Headers { get; set; }
   public string Method { get; set; }
   public PathString Path {get; set; }
   public QueryString QueryString { get; set; } 
   public IQueryCollection Query { get; set; }
}

Then I need an extension method to convert the HttpRequest to an EchoResponse -

public static class ExtensionMethods
{
   public static async Task<EchoResponse> ToEchoResponseAsync(this HttpRequest request)
   {
      var echoResponse = new EchoResponse();
      using (StreamReader streamReader = new StreamReader(request.Body))
      {
         echoResponse.Body = await streamReader.ReadToEndAsync();
      };
      echoResponse.Method = request.Method;
      echoResponse.Headers = request.Headers;
      echoResponse.Path = request.Path;
      echoResponse.QueryString = request.QueryString;
      echoResponse.Query = request.Query;
      
      return echoResponse;
   }
}

That’s the hard part done!

Minimal API Endpoint

This will map all HTTP methods to the same endpoint, for all URLs -

app.Map("{*anyurl}", async (HttpRequest httpRequest) => 
{
     return await httpRequest.ToEchoResponseAsync();
});

That’s it! Simple!

Controller

If you want to use a controller instead of an endpoint, use the following -

using Microsoft.AspNetCore.Mvc;

[ApiController]
[Route("{*anyurl}")]
public class EchoController : ControllerBase
{
    public async Task<EchoResponse> All()
    {
        return await Request.ToEchoResponseAsync();
    }
}

You should use only the minimal endpoint or the controller at one time.

Testing it out

Use tools such as Fiddler, Postman, or Rest Client for VS Code (I’ve included a sample file in the attached zip) to make requests to the API.

Download full source code.

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