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)

/// <summary>
/// Description of UseAPI.
/// </summary>
public class UseAPI
{

public UseAPI()
{
}

private const int OF_READWRITE = 2;
private const int OF_SHARE_DENY_NONE = 0x40;
private static readonly IntPtr HFILE_ERROR = new IntPtr(-1);

/// <summary>
/// 判断文件是否打开
/// </summary>
/// <param name="lpPathName">文件名称</param>
/// <param name="iReadWrite"></param>
/// <returns></returns>
[DllImport("kernel32.dll")]
private static extern IntPtr _lopen(string lpPathName, int iReadWrite);

/// <summary>
/// 关闭文件句柄
/// </summary>
/// <param name="hObject"></param>
/// <returns></returns>
[DllImport("kernel32.dll")]
private static extern bool CloseHandle(IntPtr hObject);

/// <summary>
/// 文件名称
/// </summary>
/// <param name="filename"></param>
/// <returns></returns>
public static string IsOpen(string filename)
{
IntPtr vHandle = _lopen(filename, OF_READWRITE | OF_SHARE_DENY_NONE);
if (vHandle == HFILE_ERROR)
{
CloseHandle(vHandle);
return "文件被占用！";
}
else
return "没有被占用！";

//CloseHandle(vHandle);
}
}