FormatingException was Handled

[geethaselvin]

Error : Input string was not in a correct format.

public partial class frmDealerForm : Form
    {
        DataTable t;
        DataRow r;
        string id;
        private void btnNew_Click(object sender, EventArgs e)
        {
            txtdealerID.ResetText();
            txtname.ResetText();
            txtaddress.ResetText();
            txtphoneno.ResetText();
            try
            {
                int ctr, len;
                string codeval;
                t = kalliskaBillingDataSet.Tables["DealerDetail"];
                    len = t.Rows.Count - 1;
                    r = t.Rows[len];
                    id = r["DealerID"].ToString();
                    codeval = id.Substring(1, 3);
        //Input string was not in a correct format                    
        ctr = System.Convert.ToInt32(codeval);                           
                   if ((ctr >= 1) && (ctr < 9))
                    {
                        ctr = ctr + 1;
                        txtdealerID.Text = "DE00" + ctr;
                        txtdealerID.Enabled = false;
                    }
                    else if ((ctr >= 9) && (ctr < 99))
                    {
                        ctr = ctr + 1;
                        txtdealerID.Text = "DE0" + ctr;
                        txtdealerID.Enabled = false;
                    }
                    else if (ctr >= 99)
                    {
                        ctr = ctr + 1;
                        txtdealerID.Text = "DE" + ctr;
                        txtdealerID.Enabled = false;
                    }
                }
 
            catch (IndexOutOfRangeException)
            {
                txtdealerID.Text = "DE00";
            }
            btnNew.Enabled = true;
        }

[Frinavale]

Put a break point on line 22 in the above posted code to determine what your substring is returning. It sounds like it's not returning a number.