Cross thread error in filewatcher

I have a problem here ;it's a filewatcher programm:
you enter a path in textbox,then go to that path and form example create or delete a folder then I want to log that
event

namespace filewatcherWFA
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }


        FileSystemWatcher fsw;

        public void WriteLog(string s)
        {
            // Get the Exact Location of the textFile
            string LogFilePath = Directory.GetParent(Application.ExecutablePath).ToString() + @"\Log.txt";

            //Create the StremWriter Object with FileName as Constuctor Argument and the Second Parameter is For

Weather Text is Appnded or Not
            StreamWriter sw = new StreamWriter(LogFilePath, true);

            sw.WriteLine(s);

            sw.Close();

          textBox2.Text = s+"\t";  //error occures here   ((Cross-thread)) !!

        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {

            string path=textBox1.Text;
            fsw = new FileSystemWatcher(path);
            label1.Visible = true;
            label1.Text = "path entered !";
            fsw.EnableRaisingEvents = true;
            fsw.IncludeSubdirectories = true;
            fsw.Deleted += new FileSystemEventHandler(fsw_Deleted);
            fsw.Created += new FileSystemEventHandler(fsw_Created);
        }

        void fsw_Created(object sender, FileSystemEventArgs e)
        {
            WriteLog("created File :" + e.FullPath);
        }

        void fsw_Deleted(object sender, FileSystemEventArgs e)
        {
            WriteLog("Deleted File :" + e.FullPath);
        }



    }
}

but when you are about to delete or create a folder it says::

on.>>

how can I fix that error?

Is it like in: http://social.msdn.microsoft.com/Search/en-US?query=Cross-thread%20operation%20valid%20Control%20accessed%20thread%20created&ac=8

I got that from the MSDN.

That's easy. Your file watcher is in a thread different from the form, and forms are not thread-safe. So .Net won't let it happen because if it did, you could have an error that would more difficult to diagnose. Instead, it gives the error message that is easy to solve. See: How to: Make Thread-Safe Calls to Windows Forms Controls. The following is written for just one textbox and since you have two textboxex, you need to modify the following accordingly.

In your Form class, add the member:

delegate void SetTextCallback(string text);

Then create a method:

private void SetText2(string text)
{
if (textBox2.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText2);
this.Invoke(d, new object[] { text });
}
else
{
textBox2.Text = text;
}
}

Then instead of:

textBox2.Text = s+"\t";

Do:

SetText2(s+"\t");

1 Reply

Know the answer? Post it — somebody with the same question will find it here.

Sam Hobbs16y ago
Accepted answer
Is it like in: http://social.msdn.microsoft.com/Search/en-US?query=Cross-thread%20operation%20valid%20Control%20accessed%20thread%20created&ac=8

I got that from the MSDN.

That's easy. Your file watcher is in a thread different from the form, and forms are not thread-safe. So .Net won't let it happen because if it did, you could have an error that would more difficult to diagnose. Instead, it gives the error message that is easy to solve. See: How to: Make Thread-Safe Calls to Windows Forms Controls. The following is written for just one textbox and since you have two textboxex, you need to modify the following accordingly.

In your Form class, add the member:
delegate void SetTextCallback(string text);
Then create a method:
private void SetText2(string text)
{
if (textBox2.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText2);
this.Invoke(d, new object[] { text });
}
else
{
textBox2.Text = text;
}
}
Then instead of:
textBox2.Text = s+"\t";
Do:
SetText2(s+"\t");