I have 1 app. 2 Forms are MainFrm and PopupFrm, 1 thread to update some information to PopupFrm

Now to update PopupFrm i use:

In MainFrm.cs

private PopupFrm mypop;
MainFrm()
{
    ....
    PopupFrm mypop= new PopupFrm();
    mypop.Show();
}

MyThread()
{
    Process GetData();...
    mypop.Update();
    ...
}

In PopupFrm.cs

public void Update()
{
    this.Invoke((MethodInvoker)delegate
    ....
     });
}

Problem here that mypopup alway display when MainFrm display (Start application not when has data to update). So i change MainFrm.cs to :

private PopupFrm mypop;
private bool firstdisplay=false;
MainFrm()
{
    ....
    PopupFrm mypop= new PopupFrm();
    //mypop.Show();
}

MyThread()
{
    Process GetData();...
    if(!firstdisplay)
    {
        mypop.Show();
        firstdisplay=true;
    }
    mypop.Update();
    ...
}

But it can not update Popup GUI. So how can i fix this issue ?

Thanks all.