WM_COPYDATA Message

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An application sends the WM_COPYDATA message to pass data to another application.

Syntax

To send this message, call the SendMessage function as follows.

lResult = SendMessage(    // returns LRESULT in lResult   (HWND) hWndControl,    // handle to destination control   (UINT) WM_COPYDATA,    // message ID   (WPARAM) wParam,    // = (WPARAM) () wParam;   (LPARAM) lParam    // = (LPARAM) () lParam;); 

Parameters

wParam

Handle to the window passing the data.

lParam

Pointer to a COPYDATASTRUCT structure that contains the data to be passed.

Return Value

If the receiving application processes this message, it should return TRUE; otherwise, it should return FALSE.

Remarks

The data being passed must not contain pointers or other references to objects not accessible to the application receiving the data.

While this message is being sent, the referenced data must not be changed by another thread of the sending process.

The receiving application should consider the data read-only. The lParam parameter is valid only during the processing of the message. The receiving application should not free the memory referenced bylParam. If the receiving application must access the data after SendMessage returns, it must copy the data into a local buffer.

For an example, see Using Data Copy.

Message Information

HeaderDeclared in Winuser.h, include Windows.hMinimum operating systemsWindows 95, Windows NT 3.1

See Also

SendMessage, COPYDATASTRUCT

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COPYDATASTRUCT Structure

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The COPYDATASTRUCT structure contains data to be passed to another application by the WM_COPYDATA message.

Syntax

typedef struct tagCOPYDATASTRUCT {    ULONG_PTR dwData;    DWORD cbData;    PVOID lpData;} COPYDATASTRUCT, *PCOPYDATASTRUCT;

Members

dwData

Specifies data to be passed to the receiving application.

cbData

Specifies the size, in bytes, of the data pointed to by the lpData member.

lpData

Pointer to data to be passed to the receiving application. This member can be NULL.

Structure Information

HeaderDeclared in Winuser.h, include Windows.hMinimum operating systemsWindows 95, Windows NT 3.1

See Also

WM_COPYDATA