如何從網絡共享文件中獲取關聯圖標

Question

我正在使用Icon.ExtractAssociatedIcon獲取用戶在openfiledialog中選擇的文件圖標。

的問題是，如果用戶從網絡共享的圖標，然後在打開文件對話框的文件名屬性是UNC格式，這會導致ArgumentException在ExtractAssocaitedIcon：

Value of '\\server\share\filename' is not valid for 'filePath'. 

Stack Trace: 
    at System.Drawing.Icon.ExtractAssociatedIcon(String filePath, Int32 index) 

所以我的問題是給定一個文件指定爲\\server\share\filename，我如何獲得圖標？

注： .NET 2.0

Answer 1

用Reflector看這個，它最終在shell32.dll中叫ExtractAssociatedIcon。

您是否嘗試過通過PInvoke訪問BCL？

示例代碼（通過PInvoke.Net）：

[DllImport("shell32.dll", CharSet = CharSet.Unicode)] 
static extern IntPtr ExtractAssociatedIcon(IntPtr hInst, StringBuilder lpIconPath, 
    out ushort lpiIcon); 

// ... snip 
    ushort uicon; 
    StringBuilder strB = new StringBuilder(260); // Allocate MAX_PATH chars 
    strB.Append(openFileDialog1.FileName); 
    IntPtr handle = ExtractAssociatedIcon(IntPtr.Zero, strB, out uicon); 
    Icon ico = Icon.FromHandle(handle); 

    pictureBox1.Image = ico.ToBitmap(); 
// ... snip 

Answer 2

一種方法來完成，這是檢索您的UNC路徑，並暫時將其映射到一個驅動器號，然後使用該驅動器在您的.ExtractAssociatedIcon方法。當您檢索到圖標時，您可以取消映射該驅動器。 這不是優雅，但它應該工作得很好。

Answer 3

另一種選擇是，以在用戶選擇的文件複製到它們的％TEMP％並使用Icon.ExtractAssociatedIcon那裏。只記得自己清理一下。

如果你支持大文件，顯然不是一個好的解決方案！

Answer 4

爲了完整起見，這裏是一個ExtractAssociatedIcon例行的作品：

/// <summary> 
/// Returns an icon representation of an image contained in the specified file. 
/// This function is identical to System.Drawing.Icon.ExtractAssociatedIcon, xcept this version works. 
/// </summary> 
/// <param name="filePath">The path to the file that contains an image.</param> 
/// <returns>The System.Drawing.Icon representation of the image contained in the specified file.</returns> 
/// <exception cref="System.ArgumentException">filePath does not indicate a valid file.</exception> 
public static Icon ExtractAssociatedIcon(String filePath) 
{ 
    int index = 0; 

    Uri uri; 
    if (filePath == null) 
    { 
     throw new ArgumentException(String.Format("'{0}' is not valid for '{1}'", "null", "filePath"), "filePath"); 
    } 
    try 
    { 
     uri = new Uri(filePath); 
    } 
    catch (UriFormatException) 
    { 
     filePath = Path.GetFullPath(filePath); 
     uri = new Uri(filePath); 
    } 
    //if (uri.IsUnc) 
    //{ 
    // throw new ArgumentException(String.Format("'{0}' is not valid for '{1}'", filePath, "filePath"), "filePath"); 
    //} 
    if (uri.IsFile) 
    { 
     if (!File.Exists(filePath)) 
     { 
      //IntSecurity.DemandReadFileIO(filePath); 
      throw new FileNotFoundException(filePath); 
     } 

     StringBuilder iconPath = new StringBuilder(260); 
     iconPath.Append(filePath); 

     IntPtr handle = SafeNativeMethods.ExtractAssociatedIcon(new HandleRef(null, IntPtr.Zero), iconPath, ref index); 
     if (handle != IntPtr.Zero) 
     { 
      //IntSecurity.ObjectFromWin32Handle.Demand(); 
      return Icon.FromHandle(handle); 
     } 
    } 
    return null; 
} 


/// <summary> 
/// This class suppresses stack walks for unmanaged code permission. 
/// (System.Security.SuppressUnmanagedCodeSecurityAttribute is applied to this class.) 
/// This class is for methods that are safe for anyone to call. 
/// Callers of these methods are not required to perform a full security review to make sure that the 
/// usage is secure because the methods are harmless for any caller. 
/// </summary> 
[SuppressUnmanagedCodeSecurity] 
internal static class SafeNativeMethods 
{ 
    [DllImport("shell32.dll", EntryPoint = "ExtractAssociatedIcon", CharSet = CharSet.Auto)] 
    internal static extern IntPtr ExtractAssociatedIcon(HandleRef hInst, StringBuilder iconPath, ref int index); 
} 

注意：任何代碼發佈到公共領域。無需歸屬。