Hi all,
i use vb.net , DataGridView, dataset ( aid primary key, aname not null )...... if i want the user press add or save button can check two fields
must not null value . i already try to wirte a function but must the dataset fields aname set allow null, database can set not null. If i set aname not
allow null, my function can not run before already dispaly error ( the dataset aname can not null)
And if the user entry the current row aid, aname null , after click the top row also error
How can i do, thank you .

Private Sub StorerBindingNavigatorSaveItem_Click(ByVal sender As System.Object, _
     ByVal e As System.EventArgs) Handles CompanyBindingNavigatorSaveItem.Click
        save()
    End Sub

 Private Sub save()
        If Not UsergradeDataGridView.Rows(UsergradeDataGridView.Rows.Count - 1).Cells(0).Value Is DBNull.Value And Not UsergradeDataGridView.Rows(UsergradeDataGridView.Rows.Count - 1).Cells(1).Value Is DBNull.Value Then
            Try
                Me.Validate()
                Me.UsergradeBindingSource.EndEdit()

                Me.TableAdapterManager.UpdateAll(Me.WilsonDataSet)
            Catch ex As Exception
                MsgBox(ex.Message, MsgBoxStyle.SystemModal, "Data error!")
            Finally

            End Try
        Else

        End If
end sub


Private Sub UsergradeDataGridView_CellValidating(ByVal sender As Object, _
            ByVal e As System.Windows.Forms.DataGridViewCellValidatingEventArgs) _
            Handles UsergradeDataGridView.CellValidating

        Dim strErrMsg As String
        For i = 0 To UsergradeDataGridView.Rows.Count - 1
            UsergradeDataGridView.Rows(i).ErrorText = ""
        Next

        Try
            With UsergradeDataGridView
                If e.ColumnIndex = 0 Then
                    If CStr(e.FormattedValue).Length = 0 Then
                        strErrMsg = "Grade ID must not empty!"
                        .Rows(e.RowIndex).ErrorText = strErrMsg
                        e.Cancel = True
                        MsgBox("Grade ID must not empty!", 48, "Warning")
                    ElseIf CStr(e.FormattedValue).Length > 5 Then
                        strErrMsg = "Grade ID length must not over 5 char" 
                        .Rows(e.RowIndex).ErrorText = strErrMsg
                        e.Cancel = True
  Else
                        Dim htTable As Hashtable = New Hashtable
                        Dim iRow As Integer
                        Dim sProductID As String
                        Try
                            .Rows(iRow).ErrorText = ""

                            For iRow = 0 To .Rows.Count - 1              
                                sProductID = _
                                    Microsoft.VisualBasic.Left( _
                                    CStr(.Rows(iRow).Cells(0). _
                                    EditedFormattedValue) & Space(5), _
                                    5)
                                htTable.Add(sProductID, iRow)
                            Next
                        Catch ex As Exception
                            strErrMsg = "Grade ID must not duplicate!"
                            .Rows(e.RowIndex).ErrorText = strErrMsg
                            e.Cancel = True
                            MsgBox("Grade ID must not duplicate!", 48, "Warning")
                        End Try
                    End If
                End If

                If e.ColumnIndex = 1 Then

                    If CStr(e.FormattedValue).Length > 50 Then
                        strErrMsg = "Grade Desc. length must not over 50 char!"
                        .Rows(e.RowIndex).ErrorText = strErrMsg
                        e.Cancel = True
                        MsgBox("Grade Desc. must not over 50 char!", 48, "Warning")

                    End If
                End If
            End With

        Catch ex As Exception
            MsgBox(ex.Message, MsgBoxStyle.Information, "User Grade entry error!")
        End Try

    End Sub