Auto Generate alphanumeric Unique Id with C#

Question

Total string length is 5 chars

I have a scenario, ID starts with

A0001 and ends with A9999 then B0001 to B9999 until F0001 to f9999

after that

Answer 1

see this code

private void button1_Click(object sender, EventArgs e)
{   
    string get = label1.Text.Substring(7); //label1.text=ATHCUS-100
    MessageBox.Show(get);
    string ou="ATHCUS-"+(Convert.ToInt32(get)+1).ToString();
    label1.Text = ou.ToString();

}