C# program to Create MultiKey dictionary using Tuple

//declare a dictionary object that can hold multiple keys
var multiKeyDictionary = new Dictionary<Tuple<string, string>, string>();

//add some data to that
Enumerable
 .Range(1, 10)
 .ToList()
 .ForEach
 (
    i => multiKeyDictionary.Add(
         new Tuple<string, string>("100" + i, "900000000" + i) //multi-key or composite-key
         , "User" + i // the values
     )

 );