// uses RNGCryptoServiceProvider to generate a fixed length API Key
public static string CreateKey(int length)
{
    string rchars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdejghijklmnopqrstuvwxyz1234567890";
    StringBuilder Sb = new StringBuilder();

    using (RNGCryptoServiceProvider Rng = new RNGCryptoServiceProvider())
    {
        byte[] Buffer = new byte[sizeof(uint)];

        while (length-- > 0)
        {
            Rng.GetBytes(Buffer);
            uint N = BitConverter.ToUInt32(Buffer, 0);
            Sb.Append(rchars[(int)(N % (uint)rchars.Length)]);
        }
    }

    return Sb.ToString();
}

// inserts a non alphanumeric characters into a key generated by CreateKey
// to output a more secure Password
public static string CreatePassword()
{
    string Chars = @"~`!@#$%^&*()\/',.?;:|";
    var RNG = new Random();

    // Select a character to insert into the password
    string Character = new String(Enumerable.Repeat(Chars, 1).Select(s => s[RNG.Next(s.Length)]).ToArray());

    // output a 9 character long password to which a single character will be added
    return CreateKey(9).Insert(RNG.Next(9), Character);
}