1、前言

在C#中判断文件是否被占用一般有两种方法，一是利用FileStream结合try...catch...finally实现，二是调用Windows API实现，下面给出两种方法的代码。

2、文件流法

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)
        {
            string filePath = @"D:\data.xlsx";
            bool occupied = IsOccupied(filePath);
            if (occupied)
            {
                Console.WriteLine("文件被占用");
            }
            else
            {
                Console.WriteLine("文件未被占用");
            }
            Console.ReadKey(true);
        }

        static bool IsOccupied(string filePath)
        {
            FileStream stream = null;
            try
            {
                stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.None);
                return false;
            }
            catch
            {
                return true;
            }
            finally
            {
                if (stream != null)
                {
                    stream.Close();
                }
            }
        }
    }
}

3、Windows API法

using System;
using System.Runtime.InteropServices;

namespace ConsoleApp3
{
    class Program
    {
        // 判断文件是否打开
        [DllImport("kernel32.dll")]
        public static extern IntPtr _lopen(string lpPathName, int iReadWrite);

        // 关闭文件句柄
        [DllImport("kernel32.dll")]
        public static extern bool CloseHandle(IntPtr hObject);

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

        static void Main(string[] args)
        {
            string filePath = @"D:\data.xlsx";
            bool occupied = IsOccupied(filePath);
            if (occupied)
            {
                Console.WriteLine("文件被占用");
            }
            else
            {
                Console.WriteLine("文件未被占用");
            }
            Console.ReadKey(true);
        }

        static bool IsOccupied(string filePath)
        {
            IntPtr handler = _lopen(filePath, OF_READWRITE | OF_SHARE_DENY_NONE);
            CloseHandle(handler);
            return handler == HFILE_ERROR;
        }
    }
}

VC++常用功能开发汇总（专栏文章列表，欢迎订阅，持续更新...）https://blog.csdn.net/chenlycly/article/details/124272585       在IM软件中发起文件发送时，如果要发送的是某word文件，并且该word文件被office打开，则会提示文件正在被占用无法发送，如下所示：

 那文件被占用到底是如何判断出来的呢&#x