Invalid thread-spanning operation while running a function in a new thread

Question

I've been trying to create a function call in a new Thread because if I use my main thread then my application get's too busy and can't be used anymore while the function is running.

Now I've been trying to create the function call inside a new Thread:

private void bunifuFlatButton2_Click(object sender, EventArgs e)
{
    Thread thread = new Thread(new ThreadStart(worker));
    thread.Start();
}

public void worker()
{
    using (var streamReader = File.OpenText(filePath))
    {
        var lines = streamReader.ReadToEnd().Split(new char[] { '\n' });
        var count = lines.Count();

        bunifuProgressBar1.MaximumValue = count;

        for (int i = 0; i < count; i++)
        {
            string[] words = lines[i].Split(':');
            string hash = mega.GenerateHash(words[0].ToLowerInvariant(), mega.PrepareKey(words[1].ToBytes()));

            bunifuCustomLabel4.Text = "Working: Total: " + count + ". Currently: " + (i + 1) + ".";
            bunifuCustomLabel4.Update();
            bunifuProgressBar1.Value = i + 1;
        }
    }
}

But now I receive the following error (Translated using google):

An unhandled exception of type 'System.InvalidOperationException' occurred in System.Windows.Forms.dll

Additional information: Invalid thread-spanning operation: Access to the bunifuCustomLabel4 control was from a thread other than the thread for which it was created.

How could I fix this error? I've been googling solutions but they didn't work also.

My latest attempt:

private void bunifuFlatButton2_Click(object sender, EventArgs e)
{
    ThreadStart asyncCall = delegate
    {
        bunifuCustomLabel4.Invoke(new MethodInvoker(worker));
    };

    Thread thread = new Thread(new ThreadStart(worker));
    thread.Start();
}

score 0 · Answer 1 · answered Feb 02 '17 at 17:56

You can't update the UI from a background thread. You'll have to invoke the update to the UI thread from the background using Control.Invoke()

When you need to update the UI, you can do something similar to this:

if (myControl.InvokeRequired)
{
    myControl.Invoke((MethodInvoker) delegate {this.Text = "Updated";});
}

Invalid thread-spanning operation while running a function in a new thread

1 Answers1