title: Check if method implements interface method marked with attribute
body: <p>Is it possible with Roslyn to figure out if a class method implements some interface method which was marked with attribute?</p>
  
  <p>Particularly in wcf we describe service contracts using interface. Each method of it should be marked with <code>OperationContractAttribute</code> like in following sample</p>
  
  <pre><code>[ServiceContract]
  public interface ISimleService
  {
      [OperationContract]
      string GetData(int value);
  }
  
  public class SimleService : ISimleService
  {
      public string GetData(int value)
      {
          return string.Format("You entered: {0}", value);
      }
  }
  </code></pre>
  
  <p>In Roslyn <code>ISymbol</code> interface provides us GetAttributes() method, but called on a <code>SimleService.GetData()</code> method it returns 0. Called on <code>ISimleService.GetData()</code> declaration it returns <code>OperationContractAttribute</code> as expected.</p>
  
  <p>So in general I have to check class hierarchy to find all interfaces implemented and then traverse hierarchy to find appropriate methods.This is a hard way and I guess there should be an easier one.</p>