Associating Data with a List Box Entry

• Microsoft Windows Software Development Kit (SDK) versions 3.0 and 3.1
• Microsoft Win32 Application Programming Interface (API) included with:

      - Microsoft Windows NT versions 3.5 and 3.51
      - Microsoft Windows 95 version 4.0
  

SUMMARY

In the Microsoft Windows graphical environment, an application can use the LB_SETITEMDATA and LB_GETITEMDATA messages to associate additional information with each entry in a list box. These messages enable an application to associate an arbitrary LONG value with each entry and to retrieve that value. This article documents how an application uses these messages.

MORE INFORMATION

In this example, the application will associate a 64-byte block of data with each list box entry. This is accomplished by allocating a global memory block and using the LB_SETITEMDATA message to associate the handle of the memory block with the appropriate list box item.

During list box initialization, the following code is executed for each list box item:

   if ((hLBData = GlobalAlloc(GMEM_MOVEABLE, 64)))
      {
      if ((lpLBData = GlobalLock(hLBData)))
         {
         // Store data in 64-byte block.

         GlobalUnlock(hLBData);
         }
      }
// NOTE: The MAKELONG is not needed on 32-bit platforms.
   SendMessage(hListBox, LB_SETITEMDATA, nIndex, MAKELONG(hLBData, 0));

// NOTE: The return from LB_GETITEMDATA is a long on 32-bit platforms.
   if ((hLBData = LOWORD(SendMessage(hListBox, LB_GETITEMDATA,
             nIndex, 0L))))
      {
      if ((lpLBData = GlobalLock(hLBData)))
         {
         // Access or manipulate the data or both.

         GlobalUnlock(hLBData);
         }
      }

   if ((hLBData = LOWORD(SendMessage(hListBox, LB_GETITEMDATA,
         nIndex, 0L))))
      GlobalFree(hLBData);