LB_SETITEMDATA 訊息解釋

最近用到ListBox的LB_SETITEMDATA訊息， 還蠻有用的。

Sets a value associated with the specified item in a list box.

Parameters

wParam

Specifies the zero-based index of the item. If this value is -1, the lParam value applies to all items in the list box.

Windows 95/Windows 98/Windows Millennium Edition (Windows Me): The wParam parameter is limited to 16-bit values. This means list boxes cannot contain more than 32,767 items. Although the number of items is restricted, the total size in bytes of the items in a list box is limited only by available memory.

lParam

Specifies the value to be associated with the item.

Return Value

If an error occurs, the return value is LB_ERR.

Remarks

If the item is in an owner-drawn list box created without the LBS_HASSTRINGS style, this message replaces the value contained in the lParam parameter of the LB_ADDSTRING or LB_INSERTSTRING message that added the item to the list box.

這個函數給每個ListBox裡的item一個繫結項目(lParam)，你只需要指定當前ListBox裡的item的index就行。

注意lparam的解釋：specifies the value to ba associated with the item. 就是說和相應的item綁定，而不是wParam裡提到的index. 所以它可以安全地在LB_ADDSTRING和LB_INSERTSTRING裡使用。也就是說當LB_ADDSTRING或LB_INSERTSTRING發生後，ListBox裡的items次序發生改變，也不會影響每個item的繫結項目。

這個訊息在給listbox排序等操作時很有用哦。