C# _lopen判断文件是否正在被使用

今天很无语，要解决一个问题，Silverlight中无法对用户打开的文件进行判断，是否打开，沙箱模式运作，出于安全性考虑，是无法获得

本地文件的绝对路径，无法调用API来判断实现这功能，最后还是用Trycatch来解决。

C#能够调用的API都能从以下网站查到：

API查询网站：http://www.webtropy.com/articles/Win32-API-DllImport-art9.asp

还是写下C# 调用系统API来实现文件判断效果:

1.命名空间：using System.Runtime.InteropServices

2. API函数 _lopen(string pathfile,int ireadwriter)

1 /// <summary>
2 /// Description of UseAPI.
3 /// </summary>
4     public class UseAPI
5     {
6
7         public UseAPI()
8         {
9         }
10
11         private const int OF_READWRITE = 2;
12         private const int OF_SHARE_DENY_NONE = 0x40;
13         private static readonly IntPtr HFILE_ERROR = new IntPtr(-1);
14
15
16         /// <summary>
17 /// 判断文件是否打开
18 /// </summary>
19 /// <param name="lpPathName">文件名称</param>
20 /// <param name="iReadWrite"></param>
21 /// <returns></returns>
22         [DllImport("kernel32.dll")]
23         private static extern IntPtr _lopen(string lpPathName, int iReadWrite);
24
25         /// <summary>
26 /// 关闭文件句柄
27 /// </summary>
28 /// <param name="hObject"></param>
29 /// <returns></returns>
30         [DllImport("kernel32.dll")]
31         private static extern bool CloseHandle(IntPtr hObject);
32
33         /// <summary>
34 /// 文件名称
35 /// </summary>
36 /// <param name="filename"></param>
37 /// <returns></returns>
38         public static string IsOpen(string filename)
39         {
40             IntPtr vHandle = _lopen(filename, OF_READWRITE | OF_SHARE_DENY_NONE);
41             if (vHandle == HFILE_ERROR)
42             {
43                 CloseHandle(vHandle);
44                 return "文件被占用！";
45             }
46             else
47                 return "没有被占用！";
48
49             //CloseHandle(vHandle);
50         }
51     }