private void OnAddSettingClick(object sender, EventArgs e) {
_viewModel.AddSetting(variableName.Text, variableValue.Text,
((string)variableTypeList.SelectedItem).EqualsOrdinal(Resources.SettingsPage_VariableType_String)
? ConfigurationSettingValueType.String
: ConfigurationSettingValueType.Expression);
UpdatePropertyGrid();
IsDirty = true;
}