private void OnOpenClick()
        {
            OpenFileDialog openFileDialog = new OpenFileDialog();

            openFileDialog.InitialDirectory = "./";
            openFileDialog.Filter           = "Circle app files (*.app)|*.app";
            openFileDialog.FilterIndex      = 2;
            openFileDialog.RestoreDirectory = true;

            if (openFileDialog.ShowDialog() == DialogResult.OK)
            {
                string circleId = FileNameToCircleId(openFileDialog.FileName);
                if (CheckIfAlreadyOpenedWindow(circleId))
                {
                    return;
                }

                Circle circle = ObjectReader.ReadFromFile <Circle>(openFileDialog.FileName);
                AddMenuCircleWindowData(OpenNewCircleWindow(openFileDialog.FileName, circleId, circle).Id, OnCircleWindowClick);
            }
        }