title: automapper, Can I auto assign Guid to UserId of my UserDTO?
body: <p>I want to assign Guid to UserId of my UserDTO if UserId is Null. Is it possible to do this in the CreateMap or creating any formatter?. I am using automapper as an attribute on my Actions in controller.</p>
  
  <pre><code>protected override void Configure()
          {
              Mapper.CreateMap&lt;User, UserDTO&gt;()
                  .ForMember(d =&gt; d.FullName, o =&gt; o.MapFrom(s =&gt; s.FirstName + " " + s.LastName));
          }
  </code></pre>