如何从另一个线程中的表单关闭新线程上的表单？

Question

I've been trying to figure this out for the past day or so.

I have a program which has Form1, and a button that spawns Form2 in a new thread.

I also have another button on Form1 that should close Form2, but since Form2 is in another thread, I cannot touch that object directly.

I could do t.Abort() but that throws an exception.

How can I gracefully touch the other thread? Do stuff to it?

For example, how do I close the form from within Form1?

I've searched google for "how to close a form from within another thread" and found several links hinting at Invoke and Delegate, but after trying some things, I obviously can't figure out how to use it properly.

Can anyone help me to understand how it would apply to the code I have, so that I can understand how they can be used? in which context, etc?

I've uploaded the project to github for your convenience: https://github.com/powercat/WindowsFormsApplication7/archive/master.zip

--

Code:

[Form1.cs]

    public void FormThread()
    {
        Application.Run(new Form2());
    }

    private void button1_Click(object sender, EventArgs e)
    {
        Thread t = new Thread(new ThreadStart(FormThread));
        t.Start();
    }

    private void button2_Click(object sender, EventArgs e)
    {

        //Need to close Form2 from here.

    }

[Form2.cs]

has the other form code.

Answer 1

In general, having two threads for two forms is not a good idea. It's almost always a better idea to have all of your forms on the main, UI thread, and move your logic and work onto background threads instead.

That being said, if the Form is being run in the separate thread, you should be able to use BeginInvoke to close it:

 otherForm.BeginInvoke(new Action(() => otherForm.Close()));

---

Edit:

In your case, you'd need to save the instance:

Form2 otherForm;
public void FormThread()
{       
    otherForm = new Form2();
    Application.Run(otherForm);
}

private void button1_Click(object sender, EventArgs e)
{
    Thread t = new Thread(new ThreadStart(FormThread));
    t.SetApartmentState(ApartmentState.STA); // THIS IS REQUIRED!
    t.Start();
}

private void button2_Click(object sender, EventArgs e)
{
    //Need to close Form2 from here.
    if (otherForm != null)
    {
       otherForm.BeginInvoke(new Action( () => otherForm.Close() ));
       otherForm = null;
    }
}