Cross-thread operation not valid in Windows Forms

Question

Could anyone help me i have a problem I'm trying to get this code to work in the background via threadpool but i cannot seem to get it to work i keep getting this error:

Cross-thread operation not valid: Control 'ListBox3' accessed
from a thread other than the thread it was created on. 

Here is the code i am using:

private void DoWork(object o)
{
    var list = ListBox3;

    var request = createRequest(TxtServer.Text, WebRequestMethods.Ftp.ListDirectory);

    using (var response = (FtpWebResponse)request.GetResponse())
    {
        using (var stream = response.GetResponseStream())
        {
            using (var reader = new StreamReader(stream, true))
            {
                while (!reader.EndOfStream)
                {
                    list.Items.Add(reader.ReadLine());
                    ResultLabel.Text = "Connected";
                }
            }
        }
    }
}

Answer 1

You need to invoke a delegate to update the list. See this MSDN example.