/// <summary>
/// Open a dialog window.
/// </summary>
/// <typeparam name="T">Dialog result type.</typeparam>
/// <param name="viewModel">Dialog view model.</param>
/// <returns>returns <typeparamref name="T"/> result.</returns>
public T OpenDialog <T>(DialogViewModelBase <T> viewModel)
{
var window = (IDialogWindow)Activator.CreateInstance(_window.GetType());
window.DataContext = viewModel ?? throw new ArgumentNullException(nameof(viewModel));
window.ShowDialog();
return(viewModel.DialogResult);
}