SendMessage无法使用WM_GETTEXT获取文本

我正在尝试使用SendMessage函数获取窗口的文本。 但是，我可以得到文本的长度，但我无法获得文本。 我猜txt（String）的types是不正确的SendMessage。 谢谢。

Const WM_SETTEXT = &HC Const WM_GETTEXT = &HD Const WM_GETTEXTLENGTH = &HE Dim hwnd As Long Dim hwnd_child As Long Dim result As Long Dim txtlen As Long Dim txt As String hwnd = FindWindow(vbNullString, "İngilizce Türkçe Sözlük") hwnd_child = FindWindowEx(hwnd, 0, "Edit", vbNullString) txtlen = SendMessage(hwnd_child, WM_GETTEXTLENGTH, 0, 0) s = Space$(txtlen + 1) result2 = SendMessage(hwnd_child, WM_GETTEXT, ByVal txtlen, txt) MsgBox txt