Question

I have a C# .Net web app and I am using the following LINQ Query to grab a distinct list of Proposals that a user either created, or has various User roles. The List to return contain dupes of the same proposal even after Union and Distinct. What am I doing wrong?

      var thereturn = FindAll(DetachedCriteria.For<Proposal>(),
                             new Order("CreateDate", false));

     //get the proposals that aUser created
     IList<Proposal> it = 
                thereturn.Where(proposal => proposal.CreatedBy.Equals(aUser)).ToList();

     //get the proposals that aUser is a BOE Author
     IList<Proposal> it2 =
          thereturn.Where(proposal =>
              proposal.BOEs.Any(boe =>
                  boe.Users.Where(a => a.Name == aUser).Any())).ToList();
     //get all other proposals that aUser is on
     IList<Proposal> it3 = 
          thereturn.Where(proposal =>
              proposal.Users.Where(o => o.Name == aUser).Any()).ToList();
     //now union with all other proposals that aUser is on
     return it3.Union(it).Union(it2).
               OrderByDescending(o=>o.CreateDate).Distinct().ToList();

Answer 1

What’s the definition of the Proposal class? You may have an issue with your default equality operator for the Proposal class. As msdn says about Distinct:

Returns distinct elements from a sequence by using the default equality comparer to compare values.

EDIT: In other words, do you have a custom implementation of Equals and/or GetHashCode?