title: C# compiler: CS0121: The call is ambiguous between the following methods or properties
body: <p>This is the craziest what I've seen since a Fody plugin ruined my assembly by emitting invalid code and control flow varied random at runtime... No Fody this time.</p>
  
  <p>Facts:</p>
  
  <ul>
  <li>The whole story is within one project. </li>
  <li>The GetMessage extension method is there since weeks... </li>
  <li>The issue is started since 2 hours, and I can not figure out what it is. </li>
  <li>There is only one GetMessage extension method.</li>
  <li><p>The error message (see the pic) lists two <em>identical</em> method specification</p>
  
  <p><code>Error  CS0121  The call is ambiguous between the following methods or properties: 'ComiCalc.Data.ExceptionExtensions.GetMessage2(System.Exception)' and 'ComiCalc.Data.ExceptionExtensions.GetMessage2(System.Exception)' ComiCalc.Data D:\2014Develop\.vsonline\ComiCalc\src\ComiCalc.Data\Services\UserService.cs    61
  </code></p></li>
  <li><p>If I change both the call, both the method definition (only 2 edits in 2 places) to GetMessage2, then I got exactly the same error message just referring to the GetMessage2.</p></li>
  <li>Using VS 2015</li>
  </ul>
  
  <p>Any ideas?</p>
  
  <p><a href="https://i.stack.imgur.com/MSvSJ.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/MSvSJ.jpg" alt="enter image description here"></a></p>
  
  <p>and here is the single one method:</p>
  
  <pre><code>namespace ComiCalc.Data
  {
  
      using System;
      using System.Data.Entity.Validation;
      using PluralTouch.DataAccess;
      // TODO: Move to PluralTouch
      public static class ExceptionExtensions
      {
          public static string GetMessage2(this Exception exception)
          {
  
              var message = exception.Message;
              if (exception is DbEntityValidationException)
              {
                  message = ((DbEntityValidationException) exception).DbEntityValidationResultToString();
              }
              return message;
          }
      }
  }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/sbn0K.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/sbn0K.jpg" alt="enter image description here"></a></p>