C#

Hi guys,
 
I am trying to check for inventory quantity in database. If quatinty entered in dispatch webform is less than inventory, the dispatch should continue. else i should see error message that dispatch quantity is more than inventory and terminate the process.
 
My code below gives the following results:
When i try dispatching quantity less than inventory, the error still pops up and the program does not continue to excecute dispatch.  i do not want this. 
 
I am implementing the code from addbutton that should insert item to gridview (only if quantity is more than inventory). 
 
 
 
 
 
 
int SelectedDPItem;
int InventoryQTY;
int DinventoryQTY;

SqlConnection Connection = new SqlConnection("Data Source=localhost;Initial Catalog=warehousedb;Integrated Security=True ");
SqlDataAdapter INVadapter = new SqlDataAdapter("Select ItemID, ItemName, Quantity FROM inventory ", Connection);

SelectedDPItem = int.Parse(DropDownListItem_D.SelectedValue.ToString());
// Open Connection
Connection.Open();
SqlCommand Inventorychkcommand = new SqlCommand(("Select Quantity FROM inventory " + ("WHERE (ItemName LIKE \'"
+ (DropDownListItem_D.Text + "\')"))), Connection);
InventoryQTY = Convert.ToInt32(Inventorychkcommand.ExecuteScalar());
DinventoryQTY = Convert.ToInt32(txtQuantity_D.Text);



if (InventoryQTY < DinventoryQTY)
{

{

ClientScript.RegisterStartupScript(this.GetType(), "key", "<script>alert('sorry , Stock Balance is less than requested quantity.')</script>");
}
}


else
{

{
// procedure of inserting the record
AddNewRecordRowToGrid();

txtwaybill_D.Enabled = false;
DropDownListTransp.Enabled = false;
txtTruckNo_D.Enabled = false;
txtDrivername_D.Enabled = false;
DropDownListEmployee_D.Enabled = false;
btnNew.Enabled = false;
btnPostDispatch.Enabled = true;

DropDownListItem_D.Enabled = false;
txtDispatchDate.Enabled = false;
txtDestn.Enabled = false;
txtQuantity_D.Enabled = false;
txtDestn.Enabled = false;
}

this.SetStyle(ControlStyles.DoubleBuffer |

ControlStyles.UserPaint |

ControlStyles.AllPaintingInWmPaint,

true);

string valueString = string.Empty;
          //List<byte> AtronBytes First 39 bytes = header
          int length = AtronBytes.Count - 39;
          for (int i = 0; i < length; i += 8) // length = 1176
          {
              int colNum;
              if (i == 0) colNum = 1;
              else colNum = i / 8 + 1;
              string column = machineDataColumnNames[colNum];
              //tempAtronBytes = copy of AtronBytes
              byte[] valueByte = tempAtronBytes.GetRange(0, 8).ToArray();
              // last byte of valueByte = checksum
              byte chkVal = Extentions.CalculateOpdrChecksum(tempAtronBytes.GetRange(0, 7).ToArray()); // 1ms
              if (chkVal == tempAtronBytes[7])// checksum test
              {
                  valueString = Encoding.ASCII.GetString(
                                tempAtronBytes.GetRange(0, 7).ToArray()).Trim();
                  // Remove value bytes and checksum:
                  tempAtronBytes.RemoveRange(0, 8);

                  SqlCeExtentions.ZakdataDatabase_Update(column, valueString, opdrString); // 87ms
                  // add to stringBuilder:
                  logAppend(column.PadRight(30), valueString);
                  //Show in richTextbox
                  if (colNum > 146)
                  {
                      logResult();
                  }
              }
              else
              {
                  MessageBox.Show("Checksum error");
                  return;
              }
          }