How do you remove repeated characters in a string

Question

I have a website which allows users to comment on photos. Of course, users leave comments like:

\'OMGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG

Answer 1

var test = "OMMMMMGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGMMM";

test.Distinct().Select(c => c.ToString()).ToList()
        .ForEach(c =>
            { 
                while (test.Contains(c + c)) 
                test = test.Replace(c + c, c); 
            }
        );