I'm modifying some code I found for drawing the ascending/ descending arrows
on a listview control from a C# project I found on www.codeguru.com.

The C# call to the SendMessage() API and the VB .NET call are giving me
different behaviors.

Here is the SendMessage() declaration in each of them:

VB .NET:
Declare Auto Function SendMessage Lib "User32" (ByVal hWnd As IntPtr, ByRef
msg As RR.Win32.HDM, ByVal wParam As Integer, ByRef hdItem As
RR.Win32.HDITEM) As Integer

C# // RR.Win32 namespace

/// from '.\PlatformSDK\Include\CommCtrl.h'

/// </summary>

public enum Base : int

{

LVM = 0x1000,

TV = 0x1100,

HDM = 0x1200,

TCM = 0x1300,

PGM = 0x1400,

ECM = 0x1500,

BCM = 0x1600,

CBM = 0x1700,

CCM = 0x2000,

NM = 0x0000,

LVN = NM - 100,

HDN = NM - 300,

EM = 0x400,

}

/// <summary>

/// from '.\PlatformSDK\Include\CommCtrl.h'

/// </summary>

public enum HDM : int

{

FIRST = Base.HDM,

GETITEMCOUNT = FIRST + 0,

INSERTITEMA = FIRST + 1,

DELETEITEM = FIRST + 2,

GETITEMA = FIRST + 3,

SETITEMA = FIRST + 4,

LAYOUT = FIRST + 5,

HITTEST = FIRST + 6,

GETITEMRECT = FIRST + 7,

SETIMAGELIST = FIRST + 8,

GETIMAGELIST = FIRST + 9,

INSERTITEMW = FIRST + 10,

GETITEMW = FIRST + 11,

SETITEMW = FIRST + 12,

ORDERTOINDEX = FIRST + 15,

CREATEDRAGIMAGE = FIRST + 16,

GETORDERARRAY = FIRST + 17,

SETORDERARRAY = FIRST + 18,

SETHOTDIVIDER = FIRST + 19,

SETBITMAPMARGIN = FIRST + 20,

GETBITMAPMARGIN = FIRST + 21,

SETFILTERCHANGETIMEOUT = FIRST + 22,

EDITFILTER = FIRST + 23,

CLEARFILTER = FIRST + 24,

}

/// <summary>

/// from '.\PlatformSDK\Include\CommCtrl.h'

/// </summary>

public enum HDF : int

{

LEFT = 0x0000,

RIGHT = 0x0001,

CENTER = 0x0002,

JUSTIFYMASK = 0x0003,

NOJUSTIFY = 0xFFFC,

RTLREADING = 0x0004,

SORTDOWN = 0x0200,

SORTUP = 0x0400,

SORTED = 0x0600,

NOSORT = 0xF1FF,

IMAGE = 0x0800,

BITMAP_ON_RIGHT = 0x1000,

BITMAP = 0x2000,

STRING = 0x4000,

OWNERDRAW = 0x8000

}

/// <summary>

/// from '.\PlatformSDK\Include\CommCtrl.h'

/// </summary>

public enum HDI : int

{

WIDTH = 0x0001,

HEIGHT = WIDTH,

TEXT = 0x0002,

FORMAT = 0x0004,

LPARAM = 0x0008,

BITMAP = 0x0010,

IMAGE = 0x0020,

DI_SETITEM = 0x0040,

ORDER = 0x0080,

FILTER = 0x0100

}

[StructLayout(LayoutKind.Sequential)]

public struct HDITEM

{

public HDI mask;

public int cxy;

public String pszText;

public IntPtr hbm;

public int cchTextMax;

public HDF fmt;

public int lParam;

public int iImage;

public int iOrder;

public uint type;

public IntPtr pvFilter;

}

[DllImport("user32.dll")]

public static extern int SendMessage(IntPtr hWnd, HDM msg, int wParam, ref
HDITEM hditem);

The weirdness is that after I explicitly set the column header glyph to
ascending, and it draws correctly. However, when I try to retrieve the
current format of the glyph using the VB .NET call and GETITEMW, the HDITEM
structure is not being populated.

If I make the same call with the same parameters to the C# version of the
function, the HDITEM structure is getting populated.

I've tested this by placing the C# call in a separate dll in my solution. I
call the VB function first, then call the C# function with the same
arguments. The VB .NET function does not populate the structure; the C#
function does.

Here is the code:

' VB .NET version of function call defined as above: GETITEMW has a value of
4619, column = 0, h = HDITEM structure

Win32.User32.SendMessage(header, RR.Win32.HDM.GETITEMW, column, h) ' does
not populate HDITEM structure with current information: specifically, that
h.fmt = 17408

'C# version of same call defined as above: same parameters as above call.

RR.Win32.User32.SendMessage(header, RR.Win32.HDM.GETITEMW, column, h) 'Does
populate HDITEM structure with current information: specifically that h.fmt
= 17408

There has to be something that I'm missing here. Can anyone help?

Thanks,

Chris