private void OpenCommandHandler()
        {
            var openDialog = new OpenFileDialog
            {
                Filter      = "Expressive Playground (.expl)|*.expl",
                Multiselect = false,
            };

            if (openDialog.ShowDialog() == true)
            {
                var xmlConfig = XElement.Load(openDialog.FileName);

                this.textEditor.Text = xmlConfig.Element("Expression")?.Value;
                var variables = xmlConfig.Element("Variables").Elements().Select(e => VariableDescriptor.FromXml(e));

                foreach (var v in variables)
                {
                    this.Variables.Add(v);
                }
            }
        }