How can you remove duplicate characters in a string?

Question

I have to implements a function that takes a string as an input and finds the non-duplicate character from this string.

So an an example is if I pass string str = \"

Answer 1

    void removeDuplicate()
    {
      string value1 = RemoveDuplicateChars("Devarajan");
    }

     static string RemoveDuplicateChars(string key)
    {
        string result = "";          
        foreach (char value in key)
            if (result.IndexOf(value) == -1)                   
                result += value;
        return result;
    }