Write function in c# to remove duplicates characters from string ?

Question 1) Write function in c# to remove duplicates characters from string ?
like:-
a) “morningstar”—-> “mornigsta”
b) “google”——> “gole”
c) “Google”——> “Gogle”

Answer:-

class Program
{
    static void Main(string[] args)
    {
        string myStr = "morningstar";
        Console.WriteLine("Initial String: " + myStr);
        var unique = new HashSet<char>(myStr);
        var Myfinalstring = "";
        foreach (char c in unique)
        {
            Myfinalstring = Myfinalstring + c;
        }
        Console.WriteLine("New String after removing duplicates: " + Myfinalstring);
        Console.ReadKey();
    }
}