How to get distinct characters?

Question

I have a code like

string code = \"AABBDDCCRRFF\";

In this code, I want to retrieve only distinct characters

The Output should be l

Answer 1

How about in linq:

var str = "AABBCCDDDDDDEEEEEFFF";
var unique = str.ToCharArray().Distinct();
Console.WriteLine("Answer: {0}.", string.Join(string.Empty, unique));