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             else47                 return "没有被占用！";48             49             //CloseHandle(vHandle);50         }51     }