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

Question

我需要 Shell32.dll 中的 ExtractAssociatedIcon 函数的工作示例。我无法让它发挥作用，我没有想法。我需要另一双眼睛来看看下面的代码。加载表单时，其图标应设置为 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

更正了

问题。它应该是 LPTStr，而不是 LPStr。

Answer 1

为什么不简单地使用 .NET 本机 Icon.ExtractAssociatedIcon 方法，它似乎可以做同样的事情？

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

附：
我尝试了你的代码，结果与你描述的相同，错误的结果。上面的代码片段似乎可以工作。

Answer 2

传入句柄肯定是错误的，EAI 的第一个参数是模块句柄，而不是图标句柄。这很有效：

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。如果您没有“index”参数，请不要使用此代码。 Icon.ExtractAssocationIcon 也能正常工作。

Answer 3

尝试 stakx 提到的原生 .NET 方法 - 我很幸运地保存了 ICO 文件（如果你保存为另一种格式，比如位图，它通常可以工作）

对于 pinvoke 这样的东西应该可以工作：（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);
}