C#判断文件是否被打开占用

using System.IO;
using System.Runtime.InteropServices;

[DllImport("kernel32.dll")]
public static extern IntPtr _lopen(string lpPathName, int iReadWrite);

[DllImport("kernel32.dll")]
public static extern bool CloseHandle(IntPtr hObject);

public const int OF_READWRITE = 2;
public const int OF_SHARE_DENY_NONE = 0x40;
public readonly IntPtr HFILE_ERROR = new IntPtr(-1);
private void button1_Click(object sender, EventArgs e)
{
string vFileName = @"c:\temp\temp.bmp";
if (!File.Exists(vFileName))
{
MessageBox.Show("文件都不存在，你就不要拿来耍了");
return;
}
IntPtr vHandle = _lopen(vFileName, OF_READWRITE | OF_SHARE_DENY_NONE);
if (vHandle == HFILE_ERROR)
{
MessageBox.Show("文件被占用！");
return;
}
CloseHandle(vHandle);
MessageBox.Show("没有被占用！");
}