The calling thread must be STA, because many UI components require this. in WPF.

I faced this issue while opening my window in WPF application.  After spending some hour on Google found I got this work around.

[STAThread]

        public void ShowPopuWindow()

        {

            try

            {

                Thread _Worker = new Thread(DisplayIncommingCallPopup);

                _Worker.SetApartmentState(ApartmentState.STA);

                _Worker.Start();

                _Worker.Join();

            }

            catch (Exception ex) {MessageBox.Show(ex.Message);}

        }

        public void DisplayIncommingCallPopup()

        {

            try

            {

                CallPopupWindow callPopupWindow = new CallPopupWindow();

                callPopupWindow.ShowDialog();

            }

            catch (Exception ex) { MessageBox.Show(ex.Message); }

        }