Need Working Example of Shell32's ExtractAssociatedIcon Function in .NET
I need a working example of the ExtractAssociatedIcon function in Shell32.dll. I cannot get it working and I am out of ideas. I need another set of eyes on the following code. When the form loads, its icon should be set to the Visual Studio icon, but all I get is the default system icon.
Imports System.Runtime.InteropServices
Public Class Form1
Public Function ExtractIcon(ByVal path As String, ByVal handle As IntPtr) As Icon
Dim oResult As Icon
Dim hIcon As IntPtr
Dim iIndex As Integer
Dim oPath As New System.Text.StringBuilder(260, 260)
oPath.Append(path)
hIcon = ExtractAssociatedIcon(handle, oPath, iIndex)
'hI开发者_开发知识库con = ExtractAssociatedIcon(handle, path, iIndex)
Dim oIcon As Icon = Icon.FromHandle(hIcon)
oResult = DirectCast(oIcon.Clone, Icon)
DestroyIcon(hIcon)
Return oResult
End Function
Public Declare Auto Function ExtractAssociatedIcon Lib "shell32" ( _
ByVal hInst As IntPtr, _
<MarshalAs(UnmanagedType.LPStr)> ByVal lpIconPath As System.Text.StringBuilder, _
ByRef lpiIcon As Integer) As IntPtr
'Public Declare Auto Function ExtractAssociatedIcon Lib "shell32" ( _
' ByVal hInst As IntPtr, _
' <MarshalAs(UnmanagedType.LPStr)> ByVal lpIconPath As String, _
' ByRef lpiIcon As Integer) As IntPtr
Friend Declare Auto Function DestroyIcon Lib "user32" (<[In]()> ByVal hIcon As IntPtr) As <MarshalAs(UnmanagedType.Bool)> Boolean
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'ExtractAssociatedIcon uses ExtractAssociatedIcon that is in Shell32.dll.
'This works, so why doesn't mine? What am I missing?
'Me.Icon = System.Drawing.Icon.ExtractAssociatedIcon("C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe")
Me.Icon = ExtractIcon("C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe", Me.Handle)
End Sub
End Class
Corrected
<MarshalAs(UnmanagedType.LPStr)>
was the problem. It should have been LPTStr
, not LPStr
.
Why not simply use the .NET native Icon.ExtractAssociatedIcon
method, which seems to do the same thing?
Me.Icon = Icon.ExtractAssociatedIcon( _
"C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe")
P.S.: I tried your code, with the same, wrong result that you described. The above code snippet seems to work though.
Passing in the handle is definitely wrong, the 1st argument to EAI is a module handle, not an icon handle. This worked well:
Imports System.Runtime.InteropServices
Imports System.ComponentModel
...
Public Shared Function ExtractIcon(ByVal path As String, Optional ByVal index As Integer = 0) As Icon
Dim handle As IntPtr = ExtractAssociatedIcon(IntPtr.Zero, path, index)
If handle = IntPtr.Zero Then Throw New Win32Exception(Marshal.GetLastWin32Error())
Dim retval As Icon = Nothing
using temp As Icon = Icon.FromHandle(handle)
retval = CType(temp.Clone(), Icon)
DestroyIcon(handle)
end using
Return retval
End Function
Private Declare Auto Function ExtractAssociatedIcon Lib "shell32" ( _
ByVal hInst As IntPtr, ByVal path As String, ByRef index As Integer) As IntPtr
Private Declare Auto Function DestroyIcon Lib "user32" (ByVal hIcon As IntPtr) As Boolean
No need for StringBuilder if the module handle is null. Don't use this code if you don't the "index" argument. Icon.ExtractAssocationIcon will work just as well.
Try the native .NET method stakx mentions - I've had back luck with it saving the ICO file though (if you save as another format, say bitmap, it normally works though)
For a pinvoke somethign like this should work: (caveat, not tested) referenced: http://social.msdn.microsoft.com/forums/en-US/csharpgeneral/thread/ecb6137c-8bda-4468-b5e0-359caeb202b1
[DllImport("Shell32.dll")]
private static extern int SHGetFileInfo( string pszPath, uint dwFileAttributes, out SHFILEINFO psfi, uint cbfileInfo, SHGFI uFlags );
[StructLayout(LayoutKind.Sequential)]
private struct SHFILEINFO
{
public SHFILEINFO(bool b)
{
hIcon = IntPtr.Zero; iIcon = 0; dwAttributes = 0; szDisplayName = ""; szTypeName = "";
}
public IntPtr hIcon;
public int iIcon;
public uint dwAttributes;
[MarshalAs(UnmanagedType.LPStr, SizeConst = 260)]
public string szDisplayName;
[MarshalAs(UnmanagedType.LPStr, SizeConst = 80)]
public string szTypeName;
};
private ExtractIcon()
{
}
private enum SHGFI
{
SmallIcon = 0x00000001,
LargeIcon = 0x00000000,
Icon = 0x00000100,
DisplayName = 0x00000200,
Typename = 0x00000400,
SysIconIndex = 0x00004000,
UseFileAttributes = 0x00000010
}
public static Icon GetIcon(string strPath, bool bSmall)
{
SHFILEINFO info = new SHFILEINFO(true);
int cbFileInfo = Marshal.SizeOf(info);
SHGFI flags;
if (bSmall)
{
flags = SHGFI.Icon | SHGFI.SmallIcon | SHGFI.UseFileAttributes;
}
else
{
flags = SHGFI.Icon | SHGFI.LargeIcon | SHGFI.UseFileAttributes;
}
SHGetFileInfo(strPath, 256, out info, (uint)cbFileInfo, flags);
return Icon.FromHandle(info.hIcon);
}
精彩评论