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CALLBACK procedure (invalid calling convention '__stdcall ' for function compiled with /clr:pure or /clr:safe)

Hi,

I try to figure out how to use Callback procedure in a C++ form
project

The following code *work* perfectly on a console project

#include "Windows.h"
BOOL CALLBACK MyEnumWindowsPr oc(HWND hwnd, LPARAM lparam)
{
// blablabla we dont care for now
return (TRUE);
}
int main()
{
EnumWindows((WN DENUMPROC) MyEnumWindowsPr oc,0);
}

But in the C++ form project it return the following error :

Error C3641: 'MyEnumWindowsP roc' : invalid calling convention
'__stdcall ' for function compiled with /clr:pure or /clr:safe

I already read a lot of post on the subject but still trying to find
an answer...

Thanks!

Mike

Sep 16 '07
10 7006
On Sep 25, 2:47 pm, "Ben Voigt [C++ MVP]" <r...@nospam.no spamwrote:
I'm still trying to make the enumwindows works and being able to
display the results of enumWindows in my form (this->listBox2->Items-
>Add(...)
using namespace System::Runtime ::InteropServic es;
BOOL CALLBACK MyEnumWindowsPr oc(HWND hwnd, LPARAM lparam)
{
//GCHandle MyThis = GCHandle::FromI ntPtr(lparam); //** not
working since LPARAM is not a IntPtr

There's a converting constructor, try GCHandle::FromI ntPtr(IntPtr(lp aram))
or else GCHandle::FromI ntPtr(IntPtr((v oid*)lparam))
//Form MyForm= gcnew System::Windows ::Forms::; // ** Dont know
how to define a new "this" instance (my form)
// GCHandle gch = GCHandle.FromIn tPtr(param);
// TextWriter tw = (TextWriter)gch .Target;
// tw.WriteLine(ha ndle);
return (TRUE);
}
// ....
GCHandle gch = GCHandle::Alloc (this);
// *** NOT WORKING :
EnumWindows(MyE numWindowsProc, GCHandle::ToInt Ptr(gch)); //** not
working since LPARAM is not a IntPtr

use GCHandle::ToInt Ptr(gch).ToPoin ter()
EnumWindows(MyE numWindowsProc, 0);
// ....
I need help to understand how to change the lparam param to a IntPtr
without having compiling errors like :
[error C4439: 'AutomationWinF orm::MyEnumWind owsProc' : function
definition with a managed type in the signature must have a __clrcall
calling convention]
when i change my the last param of my callback like this : BOOL
CALLBACK MyEnumWindowsPr oc(HWND hwnd, IntPtr lparam)
and
[error C2664: 'EnumWindows' : cannot convert parameter 1 from 'BOOL
(__stdcall *)(HWND,System: :IntPtr)' to 'WNDENUMPROC' ]
when I change the call to enumWindows like this
EnumWindows(MyE numWindowsProc, GCHandle::ToInt Ptr(gch));
Also it still not clear how to define a new instance of my form
(this) :
Really need help!...thanks!- Hide quoted text -

- Show quoted text -
Thanks for still trying to help me!....
BOOL CALLBACK MyEnumWindowsPr oc(HWND hwnd, LPARAM lparam)
{
GCHandle MyThis = GCHandle::FromI ntPtr(IntPtr(lp aram)) ;
// ** missing code here to be able to access to my form **//
MyThis->Label1->Text="blabla ";
return (TRUE);
}
// ....

GCHandle gch = GCHandle::Alloc (this);
EnumWindows(MyE numWindowsProc, GCHandle::ToInt Ptr(gch).ToPoin ter()); //
** Error **//

This code return the error Error C2664: 'EnumWindows' : cannot convert
parameter 2 from 'void *' to 'LPARAM'

instead of printing "blabla" in the label1 of my form each time the
callback proc is called for each windows.

I have no clues about how to recreate a usable form "instance" in my
callback procedure... The following code in the proc is to output to
the console but how to work with a form instead ???
GCHandle gch = GCHandle.FromIn tPtr(lparam);
TextWriter tw = (TextWriter)gch .Target;
tw.WriteLine(ha ndle);

Thanks...

Sep 30 '07 #11

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