How to generate checkbook number and cheueno automatically and show in the respective textboxes when I select the bankname in C# windows application

int id;
int chequeno;
int chqlvscount;
int chqendno;
int lastchequeno;
int totalckbno;
int ckbno;
private void FillCheckNo()
{
    SqlConnection con = new SqlConnection(connectionString);
    con.Open();
    SqlCommand cmd = new SqlCommand("SELECT [bank_Id],[bank_Chqstartno],[bank_Chqlvscount],[bank_Chqendno] FROM [ChequeManager].[dbo].[bankcheques] where bank_Id=@bankid and bank_Stat=0", con);
    cmd.Parameters.AddWithValue("@bankid", cmbBankname.SelectedValue.ToString());
    SqlCommand cmd1 = new SqlCommand("SELECT top 1 [id],[bank_Id],[ChequeNo] FROM [ChequeManager].[dbo].[Cheques] where bank_Id=@bankid order by id desc", con);
    cmd1.Parameters.AddWithValue("@bankid", cmbBankname.SelectedValue.ToString());
    SqlDataAdapter sd = new SqlDataAdapter(cmd1);
    DataTable dt1 = new DataTable();
    sd.Fill(dt1);
    SqlDataAdapter sda = new SqlDataAdapter(cmd);
    DataTable dt = new DataTable();
    sda.Fill(dt);
    if (dt.Rows.Count > 0)
    {
        DataRow row = dt.Rows[0];
        id = Convert.ToInt32(row["bank_Id"].ToString());
        chequeno = Convert.ToInt32(row["bank_Chqstartno"].ToString());
        chqlvscount = Convert.ToInt32(row["bank_Chqlvscount"].ToString());
        chqendno = Convert.ToInt32(row["bank_Chqendno"].ToString());
        if (dt1.Rows.Count > 0)
        {
            DataRow row1 = dt1.Rows[0];
            lastchequeno = Convert.ToInt32(row1["ChequeNo"].ToString());
        }

         if (lastchequeno == null || lastchequeno == 0)
        {
            lastchequeno = Convert.ToInt32(row["bank_Chqstartno"].ToString());
            txtcheckno.Text = Convert.ToString(lastchequeno);
        }
        else if (chqendno >= lastchequeno)
        {
            txtcheckno.Text = Convert.ToString(lastchequeno + 1);
            lastchequeno = lastchequeno + 1;

            if (lastchequeno > chqendno)
            {
                txtcheckno.Text = "";
                //txtcheckno.Text = Convert.ToString(lastchequeno);
            }
        }
       con.Close();
    }
}
private void FillChequeBookNo()
{
    SqlConnection con = new SqlConnection(connectionString);
    con.Open();
    SqlCommand cmd = new SqlCommand("SELECT [bank_Id],chqs_Chequebookno,count([chqs_Chequebookno]) as totalcheques  FROM [ChequeManager].[dbo].[chequedetails] where bank_Id=@bankid group by bank_Id,chqs_Chequebookno", con);
    cmd.Parameters.AddWithValue("@bankid", cmbBankname.SelectedValue.ToString());
    SqlDataAdapter sd = new SqlDataAdapter(cmd);
    DataTable dt = new DataTable();
    sd.Fill(dt);
    if (dt.Rows.Count > 0)
    {
        DataRow dr = dt.Rows[0];
        totalckbno = Convert.ToInt32(dr["totalcheques"].ToString());
        ckbno = Convert.ToInt32(dr["chqs_Chequebookno"].ToString());
        txtckbno.Text = Convert.ToString(ckbno);
    }
         if (chqlvscount == totalckbno)
        {
            txtckbno.Text =Convert.ToString(ckbno);
           // totalckbno = totalckbno + 1;
        }
          if(totalckbno>chqlvscount)
         {
            txtckbno.Text=Convert.ToString(ckbno + 1);
         }

else if (chqlvscount > totalckbno)
    {
        txtckbno.Text = Convert.ToString(ckbno);
    }
}