How to create random generating alphanumeric stirng in C#?

In this article, I will show you how to create a random generating alphanumeric stirng using asp.net C#. You can call this method by passing an integer as parameter. The specified value of the string will be a generate random string for you.

   string gString= GenerateRandomString(20);

    public string GenerateRandomString(int length)
        {
            Random rnd = new Random();
            string charPool
            = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
            System.Text.StringBuilder rs = new System.Text.StringBuilder();
            while (length-- > 0)
                rs.Append(charPool[(int)(rnd.NextDouble() *charPool.Length)]);
            return rs.ToString();
        } 

Here I have specified input parameter 20 and the output is 

B6X3EMZCWJIKU3R3686R