場景1

當使用 ShowDialog() 方式顯示視窗時，通過定義附加屬性的方式可實現在 ViewModel 中進行資料繫結(bool?)來控制子視窗的顯示和關閉

public class ExWindow
{
    public static bool? GetDialogResult(DependencyObject obj)
    {
        return (bool?)obj.GetValue(DialogResultProperty);
    }

    public static void SetDialogResult(DependencyObject obj, bool value)
    {
        obj.SetValue(DialogResultProperty, value);
    }

    // Using a DependencyProperty as the backing store for DialogResult.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty DialogResultProperty =
        DependencyProperty.RegisterAttached("DialogResult", typeof(bool?), typeof(ExWindow), new PropertyMetadata(true, (d, e) =>
        {
            var handler = d as Window;
            handler.DialogResult = e.NewValue as bool?;
        }));
}
 

• 參考地址：
  • Getting “DialogResult can be set only after Window is created and shown as dialog” when implementing WPF MVVM pattern for form closing
  • DialogResult can be set only after Window is created and shown as dialog

場景2

當主視窗的顯示和關閉也想通過在 ViewModel 中來進行控制的話可以通過事件和訊息級制來實現，具體可參考 MVVM Light 中的 Messenger 使用方式