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WM_COMPAREITEM message

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Sent to determine the relative position of a new item in the sorted list of an owner-drawn combo box or list box. Whenever the application adds a new item, the system sends this message to the owner of a combo box or list box created with the CBS_SORT or LBS_SORT style.

WM_COMPAREITEM

    WPARAM wParam;
    LPARAM lParam;

Parameters

wParam

Specifies the identifier of the control that sent the WM_COMPAREITEM message.

lParam

Pointer to a COMPAREITEMSTRUCT structure that contains the identifiers and application-supplied data for two items in the combo or list box.

Return value

The return value indicates the relative position of the two items. It may be any of the values shown in the following table.

Return code Description
Value
 Meaning
-1
 Item 1 precedes item 2 in the sorted order.
0
 Items 1 and 2 are equivalent in the sorted order.
1
 Item 1 follows item 2 in the sorted order.

Remarks

When the owner of an owner-drawn combo box or list box receives this message, the owner returns a value indicating which of the items specified by the COMPAREITEMSTRUCT structure will appear before the other. Typically, the system sends this message several times until it determines the exact position for the new item.

If a dialog box procedure handles this message, it should cast the desired return value to a BOOL and return the value directly. The DWL_MSGRESULT value set by the SetWindowLong function is ignored.

Requirements

Requirement Value
Minimum supported client
 Windows Vista [desktop apps only]
Minimum supported server
 Windows Server 2003 [desktop apps only]
Header
Winuser.h (include Windows.h)

See also

Reference

COMPAREITEMSTRUCT

Other Resources

SetWindowLong