关闭表单后，“从创建该线程的线程以外的线程访问控件”

Question

I have a problem and don't know how to solve it. I've got a Form2 which I open from my Form1 by a button click. In this form2 I do some operations on a ListView. While the operations are working in the background I want to show another form (Form3) which gets opened in that time. So I did the following:

public void method()
 {
  Form3 form3 = Form3.GetInstance();

        if (thrd == null)
        {
            thrd = new Thread(new ThreadStart(showForm));
            thrd.IsBackground = true;
            thrd.Start();
        }

        else
        {
            if (form3.InvokeRequired)
            {
                form3.Invoke((MethodInvoker)delegate()
                {
                    form3.Show();
                }
                );
            }
            else
            {
                form3.Show();
            }
        }

     //some operations getting invoked

        if (form3.InvokeRequired)
            {
                form3.Invoke((MethodInvoker)delegate()
                {
                    form3.Hide();
                }
                );
            }
            else
            {
                form3.Hide();
            }
}


   private void showForm()
    {
        Form3 form3 = Form3.GetInstance();
        Application.Run(Form3.GetInstance());
    }

And the code from the Form3:

    private static Form3 m_instance = null;
    private static object m_instanceLock = new object();

    public static Form3 GetInstance()
    {

        lock (m_instanceLock)
        {
            if (m_instance == null)
            {
                m_instance = new Form3();
            }
        }

        return m_instance;
    }

So when I open the Form2 and do my stuff there everything works fine. When I call operations that need longer then the Form3 shows up and closes when operations are done. But when I close my Form2 and then open it again (without closing Form1) then I get the Exception mentioned above in the headline at the Application.Run method. Why?

Answer 1

Ok this may not be the best way but I solved the problem now. I just had to put the code where he creates the Thread, shows the form and hides the form into my Form1. This prevents him crashing when the form gets opened a second time.