c# dictionary get all keys with same value : I have a Dictionary with Keys and Values. Is it possible to get all Key who has de same Value? 
Exemple 1=456894, 2=548962, 3=548962, 4=654876... and den get de Key 2 and 3 because it has the same value.

 ```Dictionary<int, int> doublechek = new Dictionary<int, int>();```