LINQ Lambda Expression JOIN

Join :

List1.Join(List2,
lst1=> lst1.
PK,
lst2 => lst2.FK, (lstPK,lstFK)=> new {lstPK,lstFK});

With Miltiple Column Join : 

List1.Join(List2,
lst1=> new {lst1.PK1, lst1.PK2},
lst2 =>new { lst2.FK1, lst2.FK2},
(lstPK,lstFK)=> new {lstPK,lstFK});

Left Outer Join : 

List1.GroupJoin(List2,
 lst1=> lst1.PK,
 lst2 => lst2.FK,
(lstPK,lstFK)=> new {list1 = lstPK, list2 = lstFK.DefaultIfEmpty()})
.SelectMany(lst => lst.list2
.Select(lst2 => new { List1 = lst.list1, List2 = lst2 }));