To resume what's the point, the solution should solve a simple problem in the most "elegant" way by using LINQ.
Check the orginial tip to get the point of this alternative
Using the code
Well, reading the following code should be straightforward :
List<double> myList = new List<double>();
bool differs = (myList.Distinct().Count() > 1);
Console.WriteLine( "All numbers are " + (differs? "not": "") + " the same.");