Im new to C# and I was wondering if you guys could help me out. First of all I am making a pretty simple generator. I want it to give me a default string everytime I press the generate button.(The string is 00000001008) then I want to add a random number/letter onto the end of that, this number/letter will have to be 3-9/A-F. then i want another string consisting of letters and/or numbers going 0-9 and A-F. I have the normal concept down and here is what I have so far:

```
public string GenerateRandomCode(ref int length)
{
    string charPool = "ABCDEF1234567890";
    StringBuilder rs = new StringBuilder();
    Random random = new Random();

    for (int i = 0; i < length; i++)
    {
        rs.Append(charPool[(int)(random.NextDouble() * charPool.Length)]);
    }
    return rs.ToString();
}

private void button1_Click(object sender, EventArgs e)
{
    textBox1.Text = "00000001008";
}

```