title: AutoMapper cannot convert enum to nullable int?
body: <p>I got AutoMapperMappingException exception</p>
  
  <blockquote>
    <p>Exception of type 'AutoMapper.AutoMapperMappingException' was thrown. ---> System.InvalidCastException: Invalid cast from 'DummyTypes' to 'System.Nullable`1[[System.Int32, ...</p>
  </blockquote>
  
  <p>when</p>
  
  <pre class="lang-cs prettyprint-override"><code>public enum DummyTypes : int
  {
      Foo = 1,
      Bar = 2
  }
  
  public class DummySource
  {
      public DummyTypes Dummy { get; set; }
  }
  
  public class DummyDestination
  {
      public int? Dummy { get; set; }
  }
  
  [TestMethod]
  public void MapDummy()
  {
      Mapper.CreateMap&lt;DummySource, DummyDestination&gt;();
      Mapper.AssertConfigurationIsValid();
      DummySource src = new DummySource()
      {
          Dummy = DummyTypes.Bar
      };
      Mapper.Map&lt;DummySource, DummyDestination&gt;(src);
  }
  </code></pre>
  
  <p>Should not AutoMapper map this implicitly without any extra explicit rule?</p>
  
  <p>P.S. I cannot change the definition of DummyDestination.Dummy to enum. I have to deal with such interfaces.</p>