| DDE is a way of communicating data between Visual Basic applications and applications such as Microsoft Word and Excel. This method was replaced by the OLE automation technology. Visual Basic 6.0 still supports DDE for ensuring backward compatibility. However, the Visual Basic .NET language does not support DDE. According to Microsoft, all Visual Basic applications that communicate with legacy applications that only support DDE should be maintained in Visual Basic 6.0. If the upgrade wizard is used to upgrade Visual Basic 6.0 applications that use DDE properties, events, and methods , the upgrade process gives several errors. The upgraded project cannot be compiled in Visual Basic .NET because it does not support DDR. The following DDE- related properties, methods, and events are not supported: LinkItem , LinkMode , LinkTimeOut , LinkTopic , LinkExecute , LinkPoke , LinkRequest , LinkSend , LinkClose , LinkError , LinkExecute , LinkNotify , LinkOpen . Example 8. An example of DDE in action The following Visual Basic 6.0 code illustrates a Visual Basic 6.0 application that interacts with an Excel workbook. To run this application, open Excel and type in anything in the first column (a few rows would do). The following code is in the DDE1-VB folder for this chapter:  Private Sub Form_Click() Static Row Row = Row + 1 Text1.LinkMode = 0 Text1.LinkTopic = "ExcelSheet1" Text1.LinkItem = "R" & Row & "C1" Text1.LinkMode = 1 End Sub Even though DDE is not supported in Visual Basic .NET, we can simulate the same behavior. In the Visual Basic .NET project, include the COM object Microsoft Excel 9.0 object library. The following equivalent Visual Basic .NET code is in the DDE1-VB.NET-Modified folder for this chapter: Private Sub Form1_Click(ByVal eventSender As _ System.Object, ByVal eventArgs As System.EventArgs)_ Handles MyBase.Click Dim xlApp As Excel.Application xlApp = GetObject(, "Excel.Application") Static Row As Integer Row = Row + 1 If Not xlApp.Cells(Row, 1).Value Is Nothing Then Text1.Text = xlApp.Cells(Row, 1).Value.ToString() End If End Sub These code snippets show how DDE-like functionality can be simulated in Visual Basic .NET.  | 
