I am using a code to generate an id for a table.But it is giving 'Conversion from type dbnull to type integer is not valid' exception.
Now I know that this is due to the table being an empty set.But it works properly if there is already a row in the table.
How to rectify this?
Private Sub GenerateID() Dim com As New MySqlCommand If conn.State = ConnectionState.Closed Then conn.Open() End If Try com.Connection = conn com.CommandText = "select max(right(cust_id,length(cust_id)-3)) from customer" last = com.ExecuteScalar Catch ex As Exception MsgBox(ex.Message) End Try If conn.State = ConnectionState.Open Then conn.Close() End If End Sub
Private Sub new_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click b1.Enabled = True GenerateID() last = last + 1 cid = "c" & "0" & "0" & "0" & "0" & last t1.Text = cid End Sub
When I click on 'new' button it generates an id pattern in the textbox 't1'.But it gives that dbnull exception first.
I am using mysql as backend and Visual Studio 2008 as frontend.Any ideas?