Auto alphanumeric Unique Id with C#

Question

Total string length is 5 chars. I have a scenario, ID starts with: A0001 and ends with: A9999, B0001 to B9999

Now,

• If my product (a) will have A0001, A0002, etc....
• If my product (b) will have b0001, b0002, etc....

How to create this format?

I tried:

int a;
        using (SqlCommand command2 = new SqlCommand("select * from voiceno WHERE ID = '1'", con))
        {
            con.Close();
            con.Open();

            SqlDataReader dr;
            dr = command2.ExecuteReader();
            if (dr.Read())
            {
                string val = dr["voiceno"].ToString();
                if (val == "0")
                {
                    txtinvoiceno.Text = "00001";
                }
                else
                {
                    a = Convert.ToInt32(dr["voiceno"].ToString());         
                    a = a + 1;
                    txtinvoiceno.Text = a.ToString("00000");
                }
            }

        }

My table looks like

CREATE TABLE [dbo].[voiceno](
[ID] [int] IDENTITY(1,1) NOT NULL,
[voiceno] [nvarchar](50) NULL)

Answer 1

You can have a function that gets current value and gives you the next value:

public string Next(string cur)
{
    int num = int.Parse(cur.Substring(1));
    char chr = cur[0];
    num++;
    if (num > 9999)
    {
        num = 0;
        chr++;
    }
    return chr + num.ToString().PadLeft(4, '0');
}

To make it get last one from database:

You can get the current biggest ID from database like:

select Max(id) from voiceno

Also look at Custom Auto-Generated Sequences with SQL Server

Live Demo