c#文件复制错误文件正在被其他程序使用

我有一个目录，我做/放置一些文件。当文件系统监视程序看到一个新文件时，它将该文件复制到另一个目录中。但是当我直接在dir1中创建文件时，它会关闭，说它被另一个程序使用。

我怎样才能摆脱这个问题?

下面是我的代码:

using System;
using System.IO;
using System.Configuration;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using MySql.Data.MySqlClient;
namespace ChaloSync
{
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }
    private bool pause = false;
    String source = ConfigurationManager.AppSettings[@"Directory1"];
    String target = ConfigurationManager.AppSettings[@"Directory2"];
    private void start()
    {
        pause = true;
        Start.Text = "Pause";
        fileSystemWatcher1.EnableRaisingEvents = true;
    }

    static void config()
    {
        foreach (string key in ConfigurationManager.AppSettings)
        {
            string value = ConfigurationManager.AppSettings[key];
            MessageBox.Show(value);
        }
    }
    private void fileSystemWatcher1_Changed(object sender, System.IO.FileSystemEventArgs e)
    {
            listBox1.Items.Add("File changed> " + e.FullPath + " -Date:" + DateTime.Now);
    }
    private void fileSystemWatcher1_Created(object sender, System.IO.FileSystemEventArgs e)
    {
            listBox1.Items.Add("File created> " + e.FullPath + " -Date:" + DateTime.Now);
            File.Copy(e.FullPath , Path.Combine(target,e.Name));
    }
    private void fileSystemWatcher1_Deleted(object sender, System.IO.FileSystemEventArgs e)
    {
            listBox1.Items.Add("File deleted> " + e.FullPath + " -Date:" + DateTime.Now);
    }
    private void fileSystemWatcher1_Renamed(object sender, System.IO.RenamedEventArgs e)
    {
            listBox1.Items.Add("File renamed> " + e.FullPath + " -Date:" + DateTime.Now);
    }
    private void Start_Click(object sender, EventArgs e)
    {
        fileSystemWatcher1.Path = source;
        if (!pause)
        {
            start();
        }
        else
        {
            pause = false;
            Start.Text = "Start";
            fileSystemWatcher1.EnableRaisingEvents = false;   
        }
        }
    }
}