Urgent!! Datagrid Column update problem

[Smithbr]

Hello, I am having a real problem figuring out why this code is not working in my vb.net project. I am tryig to get today's date, which is dispalyed in lbltdatedisp to insert into the paid column only if teh field is blank...in other words, i want to be able to update it and mark the date on day...go through and add a few more records, and mark those with a different date withut changing the date of those mark previously. In my access database the paid column is set as text so I did not think it whoud be a problem comparing it via ="" ( as you will see below in my code). Can anyone help me out with this... really need to have this working by the end of the day and can not see what I need to do...Thanks in advance for everything.

 

 Private Sub btnupdate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnupdate.Click

       If DsInvoice1.HasChanges Then
           If MessageBox.Show("You are about to save all changes made in the Datagrid, Continue?", "InvoiceHistory", MessageBoxButtons.OKCancel, MessageBoxIcon.Question) = DialogResult.OK Then
               'Da.Update(detail, "InvoiceHistory")
               Try
                   Dim dr As DataRow
                   For Each dr In DsInvoice1.Tables(0).Rows
                       If dr.Item("Paid") = "" Then
                           dr.Item("Paid") = lbltdatedisp.Text
                       End If

                   Next
                   OleDbDataAdapter1.Update(DsInvoice1)


                   grdComm.Refresh()
               Catch Ex As OleDbException
                   System.Diagnostics.Debug.Write(Ex.Message)
               End Try
           End If
       End If
End Sub

 

 

the error message i keep getting is An unhandled exception of type 'System.InvalidCastException' occurred in microsoft.visualbasic.dll

 

Additional information: Operator is not valid for type 'DBNull' and string "".

and it is referencing the line :

    If dr.Item("Paid") = "" Then 

[Nerseus]

If the field has never been initialized, regardless of the DataType (string in your case though), it won't be a default type (not "" for strings, not 0 for ints). Instead it will be a special NULL value, called System.DBNull.Value. Try this instead:

 

If dr.Item("Paid") = System.DBNull.Value Then
   dr.Item("Paid") = lbltdatedisp.Text
End If

 

If you think you may have put "" in some of the records, use this:

If dr.Item("Paid") = System.DBNull.Value Then
   dr.Item("Paid") = lbltdatedisp.Text
ElseIf dr.Item("Paid") = String.Empty Then
   dr.Item("Paid") = lbltdatedisp.Text
End If

 

I only changed your "" to String.Empty for the second IF.

 

-Nerseus

[Smithbr]

Thank you so much...I have been trying to figure this out for way longer than I wan to admitt....also, for anyone in the future,

The code is actually slighty differnet then above if it is going to work. It is:

If dr.Item("Paid") Is System.DBNull.Value Then

Thanks again Nerseus!

[Nerseus]

Ah, I keep forgetting that. You can do a direct compare in C#, but not in VB.

 

-Nerseus