HOWTO: Update Property Values in a Property Page

• The Microsoft Foundation Classes (MFC) included with:

      - Microsoft Visual C++, 32-bit Edition, version 4.0. 5.0
      - Microsoft OLE Control Developer's Kit (CDK) versions 2.0, 2.1, 2.2
  

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SUMMARY

To modify a property of an OLE control, you would normally change the properties value in the control's property page. However, it is possible for a property to be modifiable from more than one property page especially in development environments such as Visual Basic. In this case, when you change the property in the control's property page, you should synchronize the value in Visual Basic's Property Form. This article shows by example how to do it.

MORE INFORMATION

For example, in Visual Basic, place the Circ3 sample control on the Form page. Then click the right mouse button to select properties for the control. You will notice that the same properties can be seen in Visual Basic's Properties window. For example, one of the properties of Circ3 is the CircleOffset property. If you change this value in the Control's property page and click Apply, you will notice that the value has not been updated in Visual Basic's Properties window. To synchronize the value in both, you need to call BoundPropertyChanged(dispid) for each property you want to update.

Note that the dispid is the id of the property to update. It is usually found in the header file of the COleControl-derived class. The dispids for the Circ3 control follow:

// Dispatch and event IDs

       enum {
       //{{AFX_DISP_ID(CCirc3Ctrl)
       dispidCircleShape = 2L,
       dispidCircleOffset = 3L,
       dispidFlashColor = 1L,
       dispidNote = 4L,
       eventidClickIn = 1L,
       eventidClickOut = 2L,
       //}}AFX_DISP_ID
       };

Sample Code

/* Compile options needed: none
*/

void CCirc3Ctrl::OnCircleShapeChanged()

   SetModifiedFlag();

   // force the control to redraw itself
   InvalidateControl();

   // reset the circle offset, if necessary
   if (m_circleShape)
      SetCircleOffset(0);

   BoundPropertyChanged(dispidCircleShape);      // *ADD THIS LINE*
}

void CCirc3Ctrl::SetCircleOffset(short nNewValue)

   // Validate the specified offset value
   if ((m_circleOffset != nNewValue) && m_circleShape&&
       InBounds(nNewValue))
   {
      m_circleOffset = nNewValue;
      SetModifiedFlag();
      BoundPropertyChanged(dispidCircleOffset); // *ADD THIS LINE*
      InvalidateControl();
   }