using System;

using System.Security.Cryptography;

public class Program

{

    public static void Main()

    {

        var key = new byte[32];

        RNGCryptoServiceProvider.Create().GetBytes(key);

        var base64Secret = Convert.ToBase64String(key);

        // make safe for url

        var urlEncoded = base64Secret.TrimEnd('=').Replace('+', '-').Replace('/', '_');

​

        urlEncoded.Dump();

    }

}