How to Pass One OLE Control to Another

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic for Windows, 16-bit and 32-bit, version 4.0

SUMMARY

It is possible to pass an OLE Automation Object as a parameter to a method of a custom OLE control (.OCX). To do this, declare the OCX method to take a parameter of type IDispatch *. An OLE control is essentially an OLE Automation Object, so you can then pass one OLE Control to another using this technique.

MORE INFORMATION

In Visual Basic 4.0, all OLE controls except the intrinsic controls (TextBox, PictureBox, Label, and so on) implement an Object Property. Except for the OLE container control, this Object property refers to the primary IDispatch interface of that OLE control. So, if you pass the object property of any OLE control except the OLE container control to a method of another custom OLE control, a pointer to the primary IDispatch interface (LPDISPATCH) of the source OLE control is what is passed, so you can then access the methods and properties of the source OLE control through this LPDISPATCH inside your custom OLE control method.

If you have a method declared in your custom OLE control source code:

   void CTestCtrl::PassObject(LPDISPATCH lpDisp)
   {
       // TODO: Add your dispatch handler code here
       ...
   }

Test1.PassObject DbGrid1.Object    'Pass the DBGrid control's primary
                                   'dispatch interface to your custom
                                   'control, Test1