Webclient not getting response uri

Question

I found a strange behaviour in the webclient class. When i use the UploadValues() synchronous method i get the response uri normally, but when i use the async version UploadValuesTaskAsync() to the same url it returns the response uri as null. Why?

Example:

using (var client = new CustomWebClient())
{
    await Get(client);
    Get(client);
}

private async Task GetAsync(WebClient client)
{
      var resAsync = await client.UploadValuesTaskAsync("http://address.com", requestData); 
      //client.ResponseUri null here
}

private void Get(WebClient client)
{
    var res= client.UploadValues("http://address.com", requestData); 
     //client.ResponseUri **not** null here
}

In the GetAsync method the client.ResponseUri comes null, and not null for the UploadValues .

EDIT:

I discovered the WebClient is "customized":

so the class is:

 public class CustomWebClient : WebClient
 {
    public CookieContainer Cookies { get; private set; }
    public Uri ResponseUri { get; private set; }

    public CustomWebClient()
    {
        Cookies = new CookieContainer();
    }

    protected override WebRequest GetWebRequest(Uri address)
    {
        var request = base.GetWebRequest(address) as HttpWebRequest;
        if (request == null)
        {
            return base.GetWebRequest(address);
        }
        request.CookieContainer = Cookies;
        return request;
    }

    protected override WebResponse GetWebResponse(WebRequest request)
    {
        var response = base.GetWebResponse(request);
        ResponseUri = response.ResponseUri;
        return response;
    }
}

I checked that in the synchronous method it hits the GetWebResponse method before continous to the next line. But in the asynchronous version it not hit the GetWebResponse never.

Answer 1

Your customized class is only overriding the behavior for the synchronous WebResponse GetWebResponse(WebRequest request) method.

You need to add an override for the async version:

 protected override WebResponse GetWebResponse(WebRequest request, IAsyncResult result)
 {
     var response = base.GetWebResponse(request, result);
     ResponseUri = response.ResponseUri;
     return response;
 }