Linq Concat not defined?
var result = mappings.Where(m => m.Difficulty != Content.Difficulty).Concat(newMappings);I have Linq in my usings and setting result to only Where compiles but when I append Concat, it's saying IEnumerable<> has no definition for Concat. The types of mappings and newMappints are the same and I get recommended Concat when I type it.
