Something wrong when put "Delete " in Filesystemwatcher .Code cannot copy to destination target.

Question

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Diagnostics;

using System.Drawing;

using System.IO;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows.Forms;

namespace WMI_5

{

public partial class Form1 : Form

{

    private readonly string TargetPath = @"C:\Users\User\Documents\test\";

    FileSystemWatcher watcher = new FileSystemWatcher();

    public Form1()

    {

        InitializeComponent();

    }

    private void Form1_Load(object sender, EventArgs e)

    {

        watcher.NotifyFilter = NotifyFilters.Attributes

     | NotifyFilters.CreationTime

     | NotifyFilters.DirectoryName

     | NotifyFilters.FileName

     | NotifyFilters.LastAccess

     | NotifyFilters.LastWrite

     | NotifyFilters.Security

     | NotifyFilters.Size;

        watcher.Path = @"c:\";

        watcher.Filter = "*.*";

        watcher.Created += OnCreated;

        watcher.Error += OnError;

        watcher.EnableRaisingEvents = true;

        watcher.IncludeSubdirectories = true;

    }

    private void OnCreated(object sender, FileSystemEventArgs e)

    {

        try

        {

            FileInfo fileInfo = new FileInfo(e.FullPath);

            var targetFile = Path.Combine(TargetPath, fileInfo.Name);

            if (File.Exists(targetFile))

            {

                File.Delete(targetFile);

            }

            File.Copy(e.FullPath, targetFile, true);

            listBox1.Invoke((Action)(() => listBox1.Items.Add(e.FullPath + " copied to " + targetFile)));

        }

        catch (Exception exception)

        {

            Debug.WriteLine(exception.Message);

        }

    }

    private static void OnError(object sender, ErrorEventArgs e) => DisplayException(e.GetException());

    /// <summary>

    /// For debug purposes

    /// For a production environment write to a log file

    /// </summary>

    /// <param name="ex"></param>

    private static void DisplayException(Exception ex)

    {

        if (ex == null) return;

        Debug.WriteLine($"Message: {ex.Message}");

        Debug.WriteLine("Stacktrace:");

        Debug.WriteLine(ex.StackTrace);

        Debug.WriteLine("");

        DisplayException(ex.InnerException);

    }

}
}

we need remove this line;

                if (File.Exists(targetFile))
                {
                    File.Delete(targetFile);
                }

Answer 1

Hi @MIPAKTEH_1 , Welcome to Microsoft Q&A,

Don't check if the file exists in the OnCreated event handler and delete it manually. This is because FileSystemWatcher triggers the OnCreated event whenever a new file is created, including creating a new file by copying or moving an existing file

The third parameter true of File.Copy indicates that the target file will be overwritten, and you do not need to manually determine whether it exists. Just delete the judgment code directly.

The oncreated event can be simplified to:

private void OnCreated(object sender, FileSystemEventArgs e)
{
     try
     {
         var targetFile = Path.Combine(TargetPath, Path.GetFileName(e.FullPath));

         File.Copy(e.FullPath, targetFile, true);

         listBox1.Invoke((Action)(() => listBox1.Items.Add(e.FullPath + " copied to " + targetFile)));
     }
     catch (Exception exception)
     {
         Debug.WriteLine(exception.Message);
     }
}

Best Regards,

Jiale

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