ExtractAssociatedIcon返回null [英] ExtractAssociatedIcon returns null

问题描述

我使用了 ExtractAssociatedIcon 方法来检索文件的图标。我希望检索的用户将在他们的浏览器窗口中看到相同的图标。

 公共静态图标调用getIcon（字符串文件名） 
 {
试
 {
图标图标= Icon.ExtractAssociatedIcon（文件名）; 
返回图标; 
} 
抓
 {
返回NULL; 
} 
} 
  

这工作的99％的时间。但是，如果用户链接到文件的共享路径，如 \\SOME_SERVER\my documents\this file.pdf 则返回null。它属于通过陷阱，该文件路径是不是有效的路径错误。

这是一个有效的URI（我已经验证该文件存在，是读等），但不与X有效的完全合格的驱动器路径：\some\folder符号

我怎样才能解决这个问题，如果在所有？

感谢。

的 重新更新的

下面是我最终的解决方案。这比第一次更新更清洁。非常感谢克里斯·哈斯，他的答案是评论，而不是直接回答。如果/当他使它成为一个直接的答案，我会更新这个本身。

我仍然不得不下降到一个较低的水平，并通过C ++库提取图标，

 ＃地区的老派方法
函数[DllImport（SHELL32 
 
 
：但我唯一需要的库如下。 DLL）] 
静态外部的IntPtr ExtractAssociatedIcon（IntPtr的HINST，
 StringBuilder的lpIconPath，出USHORT lpiIcon）; 
 
公共静态图标GetIconOldSchool（字符串文件名）
 {
 USHORT uicon; 
 StringBuilder的STRB =新的StringBuilder（文件名）; 
 IntPtr的手柄= ExtractAssociatedIcon（IntPtr.Zero，STRB，出uicon）; 
 ICO图标= Icon.FromHandle（句柄）; 
 
返回ICO; 
} 
 #endregion 
  

有一次，我所定义的上述方法，调用getIcon（）方法变为：

 公共静态图标调用getIcon（字符串文件名） 
 {
试
 {
图标图标= Icon.ExtractAssociatedIcon（文件名）; 
返回图标; 
} 
抓
 {
试
 {
图标图标2 = GetIconOldSchool（文件名）; 
返回图标2; 
} 
抓
 {
返回NULL; 
} 
} 
} 
  

解决方案

检查出的 -get最相关的图标从 - 一个网络共享文件>这里链接，最终导致的 p / Invoke.net 用下面的代码：

 函数[DllImport（ SHELL32.DLL）] 
静态外部的IntPtr ExtractAssociatedIcon（IntPtr的HINST，StringBuilder的lpIconPath，出USHORT lpiIcon）; 
 
函数[DllImport（SHELL32.DLL）] 
静态外部的IntPtr ExtractIcon（IntPtr的HINST，串lpszExeFileName，INT nIconIndex）; 
  

_

  USHORT uicon; 
 StringBuilder的STRB =新的StringBuilder（YOUR_FILE_PATH）; 
 IntPtr的手柄= ExtractAssociatedIcon（this.Handle，STRB，出uicon）; 
 ICO图标= Icon.FromHandle（句柄）; 
 
返回ico.ToBitmap（）; 
  

I'm using the ExtractAssociatedIcon method to retrieve the icon for the file. My hope is to retrieve the same icon that a user would see in their explorer window.

    public static Icon GetIcon(string fileName) 
    {
        try
        {
            Icon icon = Icon.ExtractAssociatedIcon(fileName);
            return icon;
        }
        catch
        {
            return null;
        }
    }

This works 99% of the time. However, if the user has linked to a file on a shared path, such as \\SOME_SERVER\my documents\this file.pdf it returns null. It falls through the "catch" with the error that the file path is not a valid path.

It is a valid URI (I've verified the file exists, is readable, etc.), but not a valid fully-qualified drive path with the X:\some\folder notation.

How can I get around this, if at all?

Thanks.

Re-UPDATE

Here's the solution I ended up with. It's much cleaner than the first update. Many thanks to Chris Haas, whose answer was a comment, and not a direct answer. If/when he makes it a direct answer, I will update this as such.

I still had to go down to a lower level and fetch the icon through C++ libraries, but the only library I needed is listed below:

    #region Old-School method
    [DllImport("shell32.dll")]
    static extern IntPtr ExtractAssociatedIcon(IntPtr hInst, 
       StringBuilder lpIconPath, out ushort lpiIcon);

    public static Icon GetIconOldSchool(string fileName)
    {
        ushort uicon;
        StringBuilder strB = new StringBuilder(fileName);
        IntPtr handle = ExtractAssociatedIcon(IntPtr.Zero, strB, out uicon);
        Icon ico = Icon.FromHandle(handle);

        return ico;
    }
    #endregion

Once I had defined the above method, the GetIcon() method becomes:

    public static Icon GetIcon(string fileName) 
    {
        try
        {
            Icon icon = Icon.ExtractAssociatedIcon(fileName);
            return icon;
        }
        catch
        {
            try
            {
                Icon icon2 = GetIconOldSchool(fileName);
                return icon2;
            }
            catch
            {
                return null;
            }
        }
    }

解决方案

(Comment turned into post - CTIP)

Check out the link here which eventually leads to P/Invoke.net with the following code:

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

[DllImport("shell32.dll")]
static extern IntPtr ExtractIcon(IntPtr hInst, string lpszExeFileName, int nIconIndex);

_

ushort uicon;
StringBuilder strB = new StringBuilder(YOUR_FILE_PATH);
IntPtr handle = ExtractAssociatedIcon(this.Handle, strB, out uicon);
Icon ico = Icon.FromHandle(handle);

return ico.ToBitmap();

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