覆写档案只能运作一次

Question

I have a simple program that copies files and directories from one place to another. I have it set-up that if there are any exceptions (such as if access to the path is denied) it will create a log file with the error.

I have a button that when pressed, performs the copy action. Everything works fine the first time I press the button and the log file is either created or overwritten with the appropriate error messages.

However, if I press the button a second time, the text file is not overwritten and instead the error messages append. If I close out of my program and run it again, the file is overwritten on the first button press. Any thoughts would be greatly appreciated.

target is a string filepath which I'm getting from a FolderBrowserDialog and taking the selected path and setting it to a textbox. loglist is just a simple List<string> I'm using to store the error messages from any exceptions that occur during the copy process.

public partial class Form1 : Form
{

    static List<string> logList = new List<string>();

    public Form1()
    {
        InitializeComponent();
    }


    private static void CopyAll(DirectoryInfo source, DirectoryInfo target)
    {


        if (source.FullName.ToLower() == target.FullName.ToLower())
            return;

        if (Directory.Exists(target.FullName) == false)
        {
            Directory.CreateDirectory(target.FullName);
        }





        foreach (FileInfo fi in source.GetFiles())
        {
            try
            {
                fi.CopyTo(Path.Combine(target.ToString(), fi.Name), true);
            }
            catch (Exception ex)
            {
                logList.Add(ex.Message);


            }


        }

        foreach (DirectoryInfo diSourceSub in source.GetDirectories())
        {
            DirectoryInfo nextTargetSubDir = target.CreateSubdirectory(diSourceSub.Name);
            CopyAll(diSourceSub, nextTargetSubDir);

        }



    }


    private void directoryPickerBtn1_Click(object sender, EventArgs e)
    {
        FolderBrowserDialog folderDialog = new FolderBrowserDialog();

        DialogResult folderResult = folderDialog.ShowDialog();
        if (folderResult == DialogResult.OK)
        {

            directoryTextbox1.Text = folderDialog.SelectedPath;
        }


    }

    private void directoryPickerBtn2_Click(object sender, EventArgs e)
    {
        FolderBrowserDialog folderDialog = new FolderBrowserDialog();

        DialogResult folderResult = folderDialog.ShowDialog();
        if (folderResult == DialogResult.OK)
        {
            directoryTextbox2.Text = folderDialog.SelectedPath;
        }
    }

    private void copyBtn_Click(object sender, EventArgs e)
    {
        string source = (directoryTextbox1.Text);
        string target = (directoryTextbox2.Text);



        DirectoryInfo dirSource = new DirectoryInfo(source);
        DirectoryInfo dirTarget = new DirectoryInfo(target);

        try
        {
            CopyAll(dirSource, dirTarget);

            if (logList.Count > 0)
            {
                using (StreamWriter sw = new StreamWriter(target + @"\log.txt", false))
                {
                    foreach (string error in logList)
                    {
                        sw.WriteLine(error);

                    }


                }
            }


            DialogResult result = MessageBox.Show("Copy Succeeded", "Success");
            if (result == DialogResult.OK)
            {
                string myPath = dirTarget.ToString();
                System.Diagnostics.Process prc = new System.Diagnostics.Process();
                prc.StartInfo.FileName = myPath;
                prc.Start();
            }
        }
        catch (Exception)
        {
            MessageBox.Show("Copy Failed", "Failed");
        }


    }
}

}

Answer 1

From your code it seems that you never clear the logList, this means that it appears the file is being appending because the logList still contains all of the old entries.

You'll need to clear the list between copies if you only want relevant entries to that copy, either before you start copying or after you finish writing the file.

This would be better as a separate method

    try
    {
        CopyAll(dirSource, dirTarget);

        SaveLog(target + @"\log.txt");

        ClearLog();
        //...
    }

    private void SaveLog(string filename)
    {
        if (logList.Count > 0)
        {
            FileStream fs = File.Open(target + @"\log.txt", FileMode.Create);
            using (StreamWriter sw = new StreamWriter(fs))
            {
                foreach (string error in logList)
                {
                    sw.WriteLine(error);
                }
            }
        }
    }

Answer 2

As @Reza Aghaei pointed out in comments , the problem is that you do not clear the logList .

The file gets created anew every time, but each time you click the Copy button, the loglist still contains the results of the previous copy action.

So you need to clear the list when starting a new copy:

private static void CopyAll(DirectoryInfo source, DirectoryInfo target)
{
    logList.Clear();

    // ...