RemoveDuplicates.cs

public class RemoveDuplicates
{
    public string removeDuplicates(string input)
    {
        StringBuilder sb = new StringBuilder(input);
        int index=0;
        for (int i = 1; i<sb.Length; i++)
        {
            if(sb[index]!=sb[i]){   
                index++;
                sb[index]=sb[i];
            }
        }
        sb.Length=index+1;
        return sb.ToString();
    }
}