在.NET中需要Shell32的ExtractAssociatedIcon函数的工作示例

Question

我需要一个Shell32.dll中ExtractAssociatedIcon函数的工作示例。我不能让它工作，我没有想法。我需要另一组眼睛来看下面的代码。当窗体加载时，它的图标应该设置为Visual Studio图标，但我得到的只是默认的系统图标。

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)

        'hIcon = 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

已更正

<MarshalAs(UnmanagedType.LPStr)>是问题所在。它应该是LPTStr，而不是LPStr。

Answer 1

传入句柄肯定是错误的，EAI的第一个参数是一个模块句柄，而不是图标句柄。这样做效果很好：

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

如果模块句柄为空，则不需要StringBuilder。如果不使用"index“参数，请不要使用此代码。Icon.ExtractAssocationIcon也会工作得很好。

Answer 2

为什么不简单地使用.NET原生Icon.ExtractAssociatedIcon方法，它似乎做了同样的事情？

Me.Icon = Icon.ExtractAssociatedIcon( _
    "C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe")

附言:我试过你的代码，结果和你描述的一样，是错误的。不过，上面的代码片段似乎可以正常工作。

Answer 3

尝试一下stakx提到的原生.NET方法--我用它保存ICO文件很幸运(如果你保存为另一种格式，比方说位图，它通常可以工作)

对于这样的pinvoke应该可以工作：(警告，未测试)引用：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);
}