A registration form which allows two entries per month

protected void btnSubmit_Click(object sender, EventArgs e)
        {
           
            Hashtable empSession = (Hashtable)Session["UserDetails"];
            employeeno = Convert.ToInt32(empSession["EmpNo"]);
            int slno = Convert.ToInt32(get_max("select max(ID) from WFHCO_RQST")) + 1;
            string k;
            k = slno.ToString();
            string REQ_ID = "REQ" + k;
            string EMPNO = (from i in context.CLM_EMPLOYEE_MSTs
                           where i.EMPNO.Equals(Convert.ToInt32(empSession["EmpNo"].ToString()))
                           select i.EMPNO).SingleOrDefault().ToString();
            string FDate = TextBox2.Text;
            string TDate = TextBox3.Text;
            conn.Open();
            SqlCommand cmd = new SqlCommand("INSERT INTO WFHCO_RQST (PROJ_CODE,EMPNO,REQ_TYPE,STATUS,FROM_DATE,NAME,TO_DATE,NO_OF_DAYS,REASON,REQ_ID)VALUES('" + DropDownList2.SelectedValue.ToString() + "','" + EMPNO + "','" + DropDownList1.SelectedValue.ToString() + "','Awaiting Approval','" + TextBox2.Text.Trim() + "','" + TextBox3.Text.Trim() + "','" + TextBox4.Text + "','" + TextBox5.Text + "','" + REQ_ID + "')", conn);
            
            cmd.ExecuteNonQuery();
            cmd.Dispose();
            conn.Close();