GetWindowText does not work - winapi

Question

I'm trying to retrieve the text from an EDIT control using GetWindowText and GetWindowTextLength. The application retrieves the text from the window under the cursor and it works on all windows with a caption or text with the exception of the EDIT control. The EDIT control is the result window on the Windows XP Calculator, calc.exe.
Dim S As String
Dim L As Long
L = GetWindowTextLength(handle) + 1
Receiving string = GetWindowText(handle, S, L)
EDIT:
According to SPY++ the Edit class control does not receive the EM_GETSELTEXT or the WM_GETTEXT message.The code below retrieves the text from the Edit class control on the Windows XP calc.exe calculator every time that I press a button on my UI. It is not the method that I would have preferred to use, however, it accomplishes my task.
Const EM_SETSEL = &HB1
Const ES_READONLY = &H800
Const WM_COPY = &H301
Const EM_GETSELTEXT = &H43E
Const WM_GETTEXTLENGTH = &HE
Const WM_SETFOCUS As Long = &H7
Dim L As Long
L = SendMessage(EditHwnd, WM_GETTEXTLENGTH, 0&, 0)
SendMessage EditHwnd, WM_SETFOCUS, 0&, 0
SendMessage EditHwnd, EM_SETSEL, 0&, L
SendMessage EditHwnd, ES_READONLY, 0&, 0 ' read only = false
Clipboard.Clear
SendMessage EditHwnd, WM_COPY, 0&, 0
SendMessage EditHwnd, ES_READONLY, 1&, 0 ' read only = true
Receiving string = Clipboard.GetText
Clipboard.Clear

Answer 1

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function GetWindowTextLength Lib "user32" Alias "GetWindowTextLengthA" (ByVal hwnd As Long) As Long
Private Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hwnd As Long, ByVal lpString As String, ByVal cch As Long) As Long
Function GetText(handle As Long) As String
Dim S As String, L As Integer, cch As Long
L = GetWindowTextLength(handle) + 1
S = String(L, 0)
GetText = Mid(S, 1, GetWindowText(handle, S, L))
End Function
Private Sub Form_Load()
Dim hw As Long
hw = Me.hwnd
MsgBox GetText(hw)
End Sub
But it will not work with controls like EDIT, as it is written in help. ;( In order to get the text of the child window (control), try to get a list of all windows using API EnumWindows/EnumThreadWindows/GetWindowThreadProcessId, to find the desired control.
What is the name of the class to EDIT You need? What is its width and height? I could write code specifically for the search for this control.

Answer 2

this code works fine in Windows XP (virtual machine)
Private Declare Function FindWindow Lib "user32.dll" Alias "FindWindowA" _
(ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function FindWindowEx Lib "user32.dll" Alias "FindWindowExA" _
(ByVal hWnd1 As Long, ByVal hWnd2 As Long, ByVal lpsz1 As Any, ByVal lpsz2 As Any) As Long
Private Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" _
(ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByRef lParam As Any) As Long
Private Declare Function AttachThreadInput Lib "user32.dll" _
(ByVal idAttach As Long, ByVal idAttachTo As Long, ByVal fAttach As Long) As Long
Private Const WM_GETTEXT As Long = &HD&
Private Const WM_GETTEXTLENGTH As Long = &HE&
Function WindowText(ByVal hWnd As Long) As String
Dim ret As Long
ret = SendMessage(hWnd, WM_GETTEXTLENGTH, 0, ByVal 0&)
WindowText = String(ret, 0)
ret = SendMessage(hWnd, WM_GETTEXT, ret + 1, ByVal WindowText)
End Function
Private Sub Command1_Click()
Dim hCalc As Long, hEdit As Long
hCalc = FindWindow("SciCalc", vbNullString)
hEdit = FindWindowEx(hCalc, 0&, "Edit", vbNullString)
MsgBox WindowText(hEdit)
End Sub