Inner joining to list using Linq

I am try to inner join to list, I am struggline , can someone assist me.



                                                   var groupList = from List1 in List1.AsEnumerable()
                                                                         join List2 in List2.AsEnumerable()
                                                                         on new
                                                                         {
                                                                             KEY1 = List1.ConcatString,
                                                                             KEY2 = List1.CreationWriteTime
                                                                         }
                                                                         equals new
                                                                         {
                                                                             KEY1 = List2.ConcatString,
                                                                             KEY2 = List2.CreationWriteTime
                                                                         }
                                                                         select List2;