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maloriopolium

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LVM_SORTITEMS

Urgent!

Can anybody help me call the LVM_SORTITEMS windows message in .NET?
I'm trying to make a call to the Win32 API directly through using SendMessage. Does anyone know how to do this?

Greatly appreciated.
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jkr
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You can do that// =============================================================
// Comparison routine for sorting ListView on a column
// =============================================================
int CALLBACK ListViewCompareProc(LPARAM lParam1, LPARAM lParam2,
LPARAM lParamSort )
{
      int iResult;

   // MessageBox( hwnd, "Doing sort compare", "SortMsg", MB_OK );
   
      switch( lParamSort )
   {
         case 0:                                                // sub-item 0; file name
            iResult = 0;
            break;

      case 1:                                                // sub-item 1; folder size
      case 2:                                                // sub-item 2; number of files
            if ( lParam1 > lParam2 )
               iResult = 1;
         else
         if ( lParam1 < lParam2 )
               iResult = -1;
         else
               iResult = 0;
         break;
   }


   
   return iResult;
}


SendMessage( hwndList, LVM_SORTITEMS,(WPARAM)(LPARAM)(nSomeId),(LPARAM)(PFNLVCOMPARE)ListViewCompareProc );
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maloriopolium

ASKER

Hi jkr,

I am trying to do this in C# .NET. Can this be done? I know you can make various other Win32 API calls in C# but just not sure how to go about this one since one of the parameters is a pointer to a function (PFNLVCOMPARE)

Thanks.
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jkr
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Thanks jkr,

I just read that article you linked, it sys,
"Callback functions and passing arrays as parameters involve some more complications and can be the subject for the next article."

which sort of implies that it IS possible to pass function pointers to C#?
Do you know or can anyone point me to something that discusses the passing of callback functions or function pointers as a parameter to a Win32 API function??

Much appreciated
No, function pointer require native Win32 modules. Since C# is a P-code language (which means that it is interpreted to some extent), there are no memory addresses that resemble assembly code which could serve as a function pointer. That's why you need P/Invoke as an intermediate layer that provides these.
Can you explain what it means by using P/Invoke? It seems that all I have to do is declare the attribute:
[DllImport("user32.dll")]

and then declare a
static extern int SendMessage(....)
function which should be that of the Win32 API function.
Is that all there is to using P/Invoke?

Yes, that pretty much is it. However, I'd suggest to have the DLL that exposes the callback function itself call 'SendMessage()', since you need to have a native module pass that function pointer, managed modules won't be able to get that one.