LINQ query with Distinct and Union

Question

I currently have 2 queries that are returning lists of MyModel like this:

var q1 = ....
         select new MyModel()
         {
             TheData1 = ...
         


        

Answer 1

As was pointed out if you are combining the lists with .Union() you will have to define uniqueness by using the overload passing an IEqualityComparer for your type.

var result = q1.Union(q2, myEqualityComparer);

otherwise, and easier you could use DistinctBy( x=> x.TheUniqueId) from the MoreLinq project:

var result = q1.Concat(q2).DistinctBy(c => c.TheUniqueID);