Checking inventory level before issuing order.

After i enter quantity greater than inventory in database, i should get the error and this works fine. but my problem is that even after changing the quantity to lower than inventory, the error still pops up and cannot allow insert to proceed. 

 

 

 

SqlConnection Connection = new SqlConnection("Data Source=localhost;Initial Catalog=warehousedb;Integrated Security=True ");

SqlDataAdapter INVadapter = new SqlDataAdapter("Select ItemID, ItemName, Quantity FROM inventory ", Connection);

int SelectedDPItem;

int InventoryQTY;

int DinventoryQTY;

//SelectedDPItem = Convert.ToInt32(DropDownListItem_D.SelectedValue);

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);

Connection.Close();

if (InventoryQTY == 0 || InventoryQTY < DinventoryQTY)

ClientScript.RegisterStartupScript(this.GetType(), "key", "");

else