Taking union of two lists based on column

Question

I am taking a union of two lists using Linq to Sql. Using List1 and List2:

 var tr = List1.Union(List2).ToList();

Union works fine, but the pro

Answer 1

You should use this Union() overload (with a custom equality comparer) , or something like this:

list1.Concat(list2).GroupBy(x => x.DateProperty).Select(m => m.First());

The first solution is certainly more efficient.