C# Method Not Found when async returning Exception

Question

I receive an Exception (Method not found) when attempting to call the following method.

    public static async Task<HttpResponseMessage> Send(HttpRequestMessage request) {

        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

        HttpResponseMessage response = await HttpClient.SendAsync(request);

        if (response.IsSuccessStatusCode)
            return response;

        throw new HttpResponseException(response);
    }

The failure occurs because of the explicit exception throw on the last line.

If I change

throw new HttpResponseException(response);

to

return null;

the method is found.

I'd like to understand the specific reason the method cannot be found when attempting to throw the exception (The generic / async / TaskAwaiter is not able to match all code paths?).

Can you recommend how I can code the method in a way that I can properly throw the exception?

Thanks for your help!

MarcusTheShogun · Accepted Answer · 2018-04-20 15:17:05Z

4

This turned out to be a red herring. The problem is not related to the method signature, generics, or asynchronous operations. It is instead a .Net Standard Versioning issue the is outlined here:

Why "Method not found: 'Void System.Web.Http.HttpResponseException..ctor" after package update?

Adding the following binding redirect solved the issue:

  <dependentAssembly>
    <assemblyIdentity name="System.Net.Http" culture="neutral" publicKeyToken="b03f5f7f11d50a3a" />
    <bindingRedirect oldVersion="0.0.0.0-4.2.0.0" newVersion="4.2.0.0" />
  </dependentAssembly>

answered Apr 20, 2018 at 15:17

MarcusTheShogun

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