OFNOTIY Struct from lParam pointer

S

SpotNet

Hi Newsgroup,

While trying to customise my common dialogs and learn C#, I'm having trouble
getting this to work;

OFNOTIFY ofny = (OFNOTIFY)Marshal.PtrToStructure(lParam, typeof(OFNOTIFY));

Under the "case CDN_FOLDERCHANGE:" switch. I haven't seen this in any C#
documentation, but C++ doc's does this, in a different way like

OFNOTIFY ofny = (OFNOTIFY)lParam; (using the C++ pointer notation though).

From the same documentation I can get;

case WM_NOTIFY:
NMHDR nmhdr = (NMHDR)Marshal.PtrToStructure(lParam, typeof(NMHDR));

and

case WM_INITDIALOG:
ofn = (OPENFILENAME)Marshal.PtrToStructure(lParam,
typeof(OPENFILENAME));

to work well translating it from the C++ doc's from the web, but can't get
the OFNOTIFY, despite it stating this structure comes from lParam in the
hook proc under the CDN_FOLDERCHANGE switch message.

My Hook proc is typically defined as;
[PermissionSet(SecurityAction.Demand, Name = "FullTrust")]
protected IntPtr HookProc(IntPtr hWnd, int iMsg, IntPtr wParam, IntPtr
lParam)

Can some one point me in the correct direction on what I'm missing. I'm
thinking C++ programmers have it all, wish I knew it (as well as C# too).

Regards,
- SpotNet
 
M

Mattias Sjögren

but can't get the OFNOTIFY, despite it stating this structure comes from lParam in the
hook proc under the CDN_FOLDERCHANGE switch message.
Click to expand...

So what happens when you try it? How did you declare the OFNOTIFY
struct?


Mattias
 
S

SpotNet

Hello Mattias,

OFNOTIFY, is declared, what happens is that the program freezes for about 10
seconds then throws an exception, a bit later. Also a correction it's not
the "case CDN_FOLDERCHANGE:" switch but, rather the "case CDN_SELCHANGE:"
switch I make the declaration. I'll try be as brief as possible in the code
example;

[StructLayout(LayoutKind.Sequential, Pack = 1, Size = 0, CharSet =
CharSet.Auto)]
protected internal struct NMHDR
{
internal IntPtr hwndFrom; internal UInt32 idFrom;internal UInt32 code;
}//NMHDR

[StructLayout(LayoutKind.Sequential, Pack = 1, Size = 0, CharSet =
CharSet.Auto)]
protected internal struct OFNOTIFY
{
//[MarshalAs(UnmanagedType.Struct)]
internal NMHDR hdr;
internal OPENFILENAME lpOFN;
internal string pszFile;
}//OFNOTIFY

protected internal struct OFNOTIFYEX
{
[MarshalAs(UnmanagedType.Struct)]
internal NMHDR hdr;
//[MarshalAs(UnmanagedType.LPStruct)]
internal OPENFILENAME lpOFN;
internal IntPtr psf;
internal IntPtr pidl; //Maybe null
}//OFNOTIFYEX

[StructLayout(LayoutKind.Sequential, Pack = 1, Size = 0, CharSet =
CharSet.Auto)]
protected internal class OPENFILENAME {...}//Wee al know it's contents..

protected IntPtr HookProc(IntPtr hWnd, int iMsg, IntPtr wParam, IntPtr
lParam)
{
IntPtr hwndparent = Win32API.GetParentApi(hWnd);

switch (iMsg)
{
case Win32MessageConstant.WM_INITDIALOG:
ofn = (OPENFILENAME)Marshal.PtrToStructure(lParam,
typeof(OPENFILENAME));

//All works fine here and a bit further down the track.....

case Win32MessageConstant.WM_NOTIFY:

NMHDR nmhdr = (NMHDR)Marshal.PtrToStructure(lParam,
typeof(NMHDR));
//Super!! All is good thus far

switch (nmhdr.code) //That's right "nmhdr.code" yields
appropriately
{
case CDN_SELCHANGE:
OFNOTIFY ofny =
(OFNOTIFY)Marshal.PtrToStructure(lParam, typeof(OFNOTIFY));

case CDN_INCLUDEITEM:
OFNOTIFYEX ofnyex =
(OFNOTIFYEX)Marshal.PtrToStructure(lParam, typeof(OFNOTIFYEX));



*******All goes wrong for me whenever I try OFNOTIFY and OFNOTIFYEX
Mattias**********
If I take them out and put Console.WriteLines(...); I can see when the
switch is executed. When I use them, I'm told;

-------------------------------------------------------------------------------------------------------
An unhandled exception of type 'System.NullReferenceException' occurred in
mscorlib.dll

Additional information: Object reference not set to an instance of an
object.
-------------------------------------------------------------------------------------------------------

How Rude!

}//HookProc

Hope this sheds a little more light on this Mattias, as I've said before
I've copied and 'translated' a lot of this from C++ documentation as there
no C# documatation on this. Thanks you so much as well for your reply.

Regards,
-SpotNet

:
: >but can't get the OFNOTIFY, despite it stating this structure comes from
lParam in the
: >hook proc under the CDN_FOLDERCHANGE switch message.
:
: So what happens when you try it? How did you declare the OFNOTIFY
: struct?
:
:
: Mattias
:
: --
: Mattias Sjögren [C# MVP] mattias @ mvps.org
: http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
: Please reply only to the newsgroup.
 
M

Mattias Sjögren

[StructLayout(LayoutKind.Sequential, Pack = 1, Size = 0, CharSet =
CharSet.Auto)]
protected internal struct OFNOTIFY
{
//[MarshalAs(UnmanagedType.Struct)]
internal NMHDR hdr;
internal OPENFILENAME lpOFN;
internal string pszFile;
}//OFNOTIFY
Click to expand...

Why do you set Size=0 in the StructLayout attribute?

The lpOFN member should be a pointer to an OPENFILENAME struct, it
should not contain the struct inline. So it's better represented as an
IntPtr. I suspect that's what causing the exception.

Since the docs say that pdzFile is only valid for CDN_SHAREVIOLATION,
I'd change that to an IntPtr as well. That would ensure that the CLR
doesn't attempt to dereference a possibly invalid string pointer.

protected internal class OPENFILENAME {...}//Wee al know it's contents..
Click to expand...

Well I know what _should_ be the content, but I don't know how you
declared it. By leaving out importand parts of your code you're just
making it harder for us to help you find any errors.



Mattias
 
S

SpotNet

Hello Mattias,

Indeed it works and well. Size = 0, I got off someone else's example (in
C++) now removed, specific structures have been changed to IntPtr's and all
works well. Just for the sake of it, my OPENFILENAME class looks like;

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
protected internal class OPENFILENAME
{
internal Int32 lStructSize = 0;
internal IntPtr hwndOwner = IntPtr.Zero;
internal IntPtr hInstance = IntPtr.Zero;
internal string lpstrFilter = null;
internal string lpstrCustomFilter = null;
internal Int32 nMaxCustFilter = 0;
internal Int32 nFilterIndex = 0;
internal string lpstrFile = null;
internal Int32 nMaxFile = 0;
internal string lpstrFileTitle = null;
internal Int32 nMaxFileTitle = 0;
internal string lpstrInitialDir = null;
internal string lpstrTitle = null;
internal Int32 Flags = 0;
internal Int16 nFileOffset = 0;
internal Int16 nFileExtension = 0;
internal string lpstrDefExt = null;
internal IntPtr lCustData = IntPtr.Zero;
internal OFNHookProc lpfnHook = null;
internal string lpTemplateName = null;
internal IntPtr pvReserved = IntPtr.Zero;
internal Int32 dwReserved = 0;
internal Int32 FlagsEx = 0;
}//OPENFILENAME

Thanks so much Mattias and you've help me to realise how much more I need to
learn, with great enjoyment ;~). There seems to be alot of C++ and VB.NET
examples of the common dialogs from Google searches, neither of which seem
to work when a 'direct (indirect) translation' is applied to C#.

Many thanks Mattias.

Regards,
- SpotNet


:
: >[StructLayout(LayoutKind.Sequential, Pack = 1, Size = 0, CharSet =
: >CharSet.Auto)]
: >protected internal struct OFNOTIFY
: >{
: > //[MarshalAs(UnmanagedType.Struct)]
: > internal NMHDR hdr;
: > internal OPENFILENAME lpOFN;
: > internal string pszFile;
: >}//OFNOTIFY
:
: Why do you set Size=0 in the StructLayout attribute?
:
: The lpOFN member should be a pointer to an OPENFILENAME struct, it
: should not contain the struct inline. So it's better represented as an
: IntPtr. I suspect that's what causing the exception.
:
: Since the docs say that pdzFile is only valid for CDN_SHAREVIOLATION,
: I'd change that to an IntPtr as well. That would ensure that the CLR
: doesn't attempt to dereference a possibly invalid string pointer.
:
:
: >protected internal class OPENFILENAME {...}//Wee al know it's contents..
:
: Well I know what _should_ be the content, but I don't know how you
: declared it. By leaving out importand parts of your code you're just
: making it harder for us to help you find any errors.
:
:
:
: Mattias
:
: --
: Mattias Sjögren [C# MVP] mattias @ mvps.org
: http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
: Please reply only to the newsgroup.
 
S

SpotNet

Hello Mattias,

Indeed it works and well. Size = 0, I got off someone else's example (in
C++) now removed, specific structures have been changed to IntPtr's and all
works well. Just for the sake of it, my OPENFILENAME class looks like;

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
protected internal class OPENFILENAME
{
internal Int32 lStructSize = 0;
internal IntPtr hwndOwner = IntPtr.Zero;
internal IntPtr hInstance = IntPtr.Zero;
internal string lpstrFilter = null;
internal string lpstrCustomFilter = null;
internal Int32 nMaxCustFilter = 0;
internal Int32 nFilterIndex = 0;
internal string lpstrFile = null;
internal Int32 nMaxFile = 0;
internal string lpstrFileTitle = null;
internal Int32 nMaxFileTitle = 0;
internal string lpstrInitialDir = null;
internal string lpstrTitle = null;
internal Int32 Flags = 0;
internal Int16 nFileOffset = 0;
internal Int16 nFileExtension = 0;
internal string lpstrDefExt = null;
internal IntPtr lCustData = IntPtr.Zero;
internal OFNHookProc lpfnHook = null;
internal string lpTemplateName = null;
internal IntPtr pvReserved = IntPtr.Zero;
internal Int32 dwReserved = 0;
internal Int32 FlagsEx = 0;
}//OPENFILENAME

Thanks so much Mattias and you've help me to realise how much more I need to
learn, with great enjoyment ;~). There seems to be alot of C++ and VB.NET
examples of the common dialogs from Google searches, neither of which seem
to work when a 'direct (indirect) translation' is applied to C#.

Many thanks Mattias.

Regards,
- SpotNet

:
: >[StructLayout(LayoutKind.Sequential, Pack = 1, Size = 0, CharSet =
: >CharSet.Auto)]
: >protected internal struct OFNOTIFY
: >{
: > //[MarshalAs(UnmanagedType.Struct)]
: > internal NMHDR hdr;
: > internal OPENFILENAME lpOFN;
: > internal string pszFile;
: >}//OFNOTIFY
:
: Why do you set Size=0 in the StructLayout attribute?
:
: The lpOFN member should be a pointer to an OPENFILENAME struct, it
: should not contain the struct inline. So it's better represented as an
: IntPtr. I suspect that's what causing the exception.
:
: Since the docs say that pdzFile is only valid for CDN_SHAREVIOLATION,
: I'd change that to an IntPtr as well. That would ensure that the CLR
: doesn't attempt to dereference a possibly invalid string pointer.
:
:
: >protected internal class OPENFILENAME {...}//Wee al know it's contents..
:
: Well I know what _should_ be the content, but I don't know how you
: declared it. By leaving out importand parts of your code you're just
: making it harder for us to help you find any errors.
:
:
:
: Mattias
:
: --
: Mattias Sjögren [C# MVP] mattias @ mvps.org
: http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
: Please reply only to the newsgroup.
 

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