Generate Strong Random Password

 -----RandomPasswordCrate.cs
public class RandomPasswordCrate
{
  private int RandomInteger(int min, int max)
    {
        RNGCryptoServiceProvider Rand = new RNGCryptoServiceProvider();
        uint scale = uint.MaxValue;
        while (scale == uint.MaxValue)
        {
            // Get four random bytes.
            byte[] four_bytes = new byte[4];
            Rand.GetBytes(four_bytes);

            // Convert that into an uint.
            scale = BitConverter.ToUInt32(four_bytes, 0);
        }

        // Add min to the scaled difference between max and min.
        return (int)(min + (max - min) *
            (scale / (double)uint.MaxValue));
    }
    private string RandomChar(string str)
    {
        return str.Substring(RandomInteger(0, str.Length - 1), 1);
    }
    private string RandomizeString(string str)
    {
        string result = "";
        while (str.Length > 0)
        {
            // Pick a random character.
            int i = RandomInteger(0, str.Length - 1);
            result += str.Substring(i, 1);
            str = str.Remove(i, 1);
        }
        return result;
    }
    private string RandomPassword(int min_chars, int max_chars)
    {
        const string LOWER = "abcdefghijklmnopqrstuvwxyz";
        const string UPPER = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        const string NUMBER = "0123456789";
        //const string SPECIAL = @"~!@#$%^&*():;[]{}<>,.?/\|";
        const string SPECIAL = @"~!@#%&_<>";

        // Make a list of allowed characters.
        string allowed = "";
        allowed += LOWER;
        allowed += UPPER;
        allowed += NUMBER;
        allowed += SPECIAL;

        // Pick the number of characters.
     
        int num_chars = RandomInteger(min_chars, max_chars);

        // Satisfy requirements.
        string password = "";

        password += RandomChar(LOWER);

        password += RandomChar(UPPER);

        password += RandomChar(NUMBER);

        password += RandomChar(SPECIAL);


        // Add the remaining characters randomly.
        while (password.Length < num_chars)
            password += allowed.Substring(
                RandomInteger(0, allowed.Length - 1), 1);

        // Randomize (to mix up the required characters at the front).
        password = RandomizeString(password);

        return password;
    }

}
------In cs Page
protected void Page_Load(object sender, EventArgs e)
{
string password = "Your password is: " + RandomPassword(9, 20);
}