please help me, what is the code ?

private void button1_Click(object sender, EventArgs e)

        {

            Random r = new Random();

            string serial = "";

            for (int i = 0; i < 14; i++)

            {

                serial += Convert.ToChar(r.Next(65, 90)).ToString();

            }

            textBox1.Text = serial;

        }

Mesha:
 
You want a Serial Number that is 14 digits?
 
Dont you have to get the starting number from somewhere?
 
Then you just increment it and save it somewhere.
 
I think you need to explain more on what you need.