Question

我想问一下使用MVVM模式和MVVMLight框架显示子窗口的最佳方法。我在这个网站上已经阅读了几个主题，但我似乎并不清楚编写的代码究竟是做什么的，所以请提供详细的解释。

Answer 1

我使用服务来显示新窗口或新对话框。

您可以查看我的第一个版本以查看对话框here

我在最后几天为我的界面添加了一些重载

public interface IUIDialogWindowService
{
    ///<summary>
    /// Zeigt ein Dialog an.
    ///</summary>
    ///<param name="titel">Titel für den Dialog</param>
    ///<param name="datacontext">DataContext für den Dialog</param>
    ///<returns>true wenn DialogResult=true, ansonsten false</returns>
    bool? ShowDialog(string titel, object datacontext);

    ///<summary>
    /// Zeigt ein Dialog an.
    ///</summary>
    ///<param name="titel">Titel für den Dialog</param>
    ///<param name="datacontext">DataContext für den Dialog</param>
    ///<param name="minHeigth">Minimum Height</param>
    ///<param name="minWidth">Minimum Width</param>
    ///<param name="maxHeigth">Maximum Height</param>
    ///<param name="maxWidth">Maximum Width</param>
    ///<returns>true wenn DialogResult=true, ansonsten false</returns>
    bool? ShowDialog(string titel, object datacontext, double minHeigth = 0, double minWidth=0, double maxHeigth = double.PositiveInfinity, double maxWidth = double.PositiveInfinity);


    /// <summary>
    /// Zeigt ein Dialog an
    /// </summary>
    /// <param name="titel">Titel für den Dialog<</param>
    /// <param name="datacontext">DataContext für den Dialog</param>
    /// <param name="settings">ApplicationsSetting für Height and Width</param>
    /// <param name="pathHeigthSetting">Name für Height Setting</param>
    /// <param name="pathWidthSetting">Name für Width Setting</param>
    /// <param name="minHeigth">Minimum Height</param>
    /// <param name="minWidth">Minimum Width</param>
    /// <param name="maxHeigth">Maximum Height</param>
    /// <param name="maxWidth">Maximum Width</param>
    /// <returns>true wenn DialogResult=true, ansonsten false</returns>
    bool? ShowDialog(string titel, object datacontext, ApplicationSettingsBase settings, string pathHeigthSetting, string pathWidthSetting, double minHeigth = 0, double minWidth = 0, double maxHeigth = double.PositiveInfinity, double maxWidth = double.PositiveInfinity);
}


///<summary>
/// Implementierung von <see cref="IUIDialogWindowService"/>
///</summary>
[PartCreationPolicy(CreationPolicy.Shared)]
[Export(typeof(IUIDialogWindowService))]
public class WpfUIDialogWindowService : IUIDialogWindowService
{
    #region Implementation of IUIDialogWindowService

    ///<summary>
    /// Zeigt ein Dialog an.
    ///</summary>
    ///<param name="titel">Titel für den Dialog</param>
    ///<param name="datacontext">DataContext für den Dialog</param>
    ///<returns>true wenn DialogResult=true, ansonsten false</returns>
    public bool? ShowDialog(string titel, object datacontext)
    {
        var win = new DialogWindow {Title = titel, DataContext = datacontext};

        return win.ShowDialog();
    }

    ///<summary>
    /// Zeigt ein Dialog an.
    ///</summary>
    ///<param name="titel">Titel für den Dialog</param>
    ///<param name="datacontext">DataContext für den Dialog</param>
    ///<param name="minHeigth">Minimum Height</param>
    ///<param name="minWidth">Minimum Width</param>
    ///<param name="maxHeigth">Maximum Height</param>
    ///<param name="maxWidth">Maximum Width</param>
    ///<returns>true wenn DialogResult=true, ansonsten false</returns>
    public bool? ShowDialog(string titel, object datacontext, double minHeigth = 0, double minWidth = 0, double maxHeigth = double.PositiveInfinity, double maxWidth = double.PositiveInfinity)
    {
        var win = new DialogWindow { Title = titel, DataContext = datacontext };

        win.MinHeight = minHeigth;
        win.MinWidth = minWidth;
        win.MaxHeight = maxHeigth;
        win.MaxWidth = maxWidth;

        return win.ShowDialog();
    }

    /// <summary>
    /// Zeigt ein Dialog an
    /// </summary>
    /// <param name="titel">Titel für den Dialog<</param>
    /// <param name="datacontext">DataContext für den Dialog</param>
    /// <param name="settings">ApplicationsSetting für Height and Width</param>
    /// <param name="pathHeigthSetting">Name für Height Setting</param>
    /// <param name="pathWidthSetting">Name für Width Setting</param>
    /// <param name="minHeigth">Minimum Height</param>
    /// <param name="minWidth">Minimum Width</param>
    /// <param name="maxHeigth">Maximum Height</param>
    /// <param name="maxWidth">Maximum Width</param>
    /// <returns>true wenn DialogResult=true, ansonsten false</returns>
    public bool? ShowDialog(string titel, object datacontext, ApplicationSettingsBase settings, string pathHeigthSetting, string pathWidthSetting, double minHeigth = 0, double minWidth = 0, double maxHeigth = double.PositiveInfinity, double maxWidth = double.PositiveInfinity)
    {
        var win = new DialogWindow { Title = titel, DataContext = datacontext };

        win.MinHeight = minHeigth;
        win.MinWidth = minWidth;
        win.MaxHeight = maxHeigth;
        win.MaxWidth = maxWidth;

        try
        {
            if(settings != null)
            {
                win.SizeToContent = SizeToContent.Manual;

                var height = settings[pathHeigthSetting];
                var width = settings[pathWidthSetting];

                BindingOperations.SetBinding(win, FrameworkElement.HeightProperty, new Binding(pathHeigthSetting) { Source = settings, Mode = BindingMode.TwoWay });
                BindingOperations.SetBinding(win, FrameworkElement.WidthProperty, new Binding(pathWidthSetting) { Source = settings, Mode = BindingMode.TwoWay });

                win.Height = (double)height;
                win.Width = (double)width;
            }
        }
        catch
        {
            win.SizeToContent = SizeToContent.WidthAndHeight;
        }

        return win.ShowDialog();
    }





    #endregion
}

为了完整起见：

<Window x:Class="DialogWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300"
    WindowStyle="SingleBorderWindow" 
    WindowStartupLocation="CenterOwner" SizeToContent="WidthAndHeight"
    Style="{DynamicResource {x:Type Window}}">
<ContentPresenter x:Name="DialogPresenter" Content="{Binding .}">

</ContentPresenter>
</Window>

public partial class DialogWindow : Window
{
    public DialogWindow()
    {
        InitializeComponent();
        this.DialogPresenter.DataContextChanged += DialogPresenterDataContextChanged;
    }



    private void DialogPresenterDataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
    {
        var d = e.NewValue as IDialogResultVMHelper;

        if (d == null)
            return;

        d.RequestCloseDialog += new EventHandler<RequestCloseDialogEventArgs>(DialogResultTrueEvent).MakeWeak(eh => d.RequestCloseDialog -= eh);
    }

    private void DialogResultTrueEvent(object sender, RequestCloseDialogEventArgs eventargs)
    {
        this.DialogResult = eventargs.DialogResult;
    }
}

public class RequestCloseDialogEventArgs : EventArgs
{
    public RequestCloseDialogEventArgs(bool dialogresult)
    {
        this.DialogResult = dialogresult;
    }

    public bool DialogResult
    {
        get; set;
    }
}

public interface IDialogResultVMHelper
{
    event EventHandler<RequestCloseDialogEventArgs> RequestCloseDialog;
}

Answer 2

首先是一个问题，一个反直觉的问题。新窗口操作与MVVM的关系是什么？

我个人认为根本没有任何联系。事实上，像其他几个UI构造一样，它完全出现在View层中。还有其他几个概念，

基于导航的界面（使用NavigationWindow），其中数据填充到表单中，并按下Next以便更改为下一页
使用一组可变操作打开的上下文菜单
动态加载活动页面的选项卡式控件

所有这些都是向用户显示新视图的不同方式。只有通过呈现绑定到ViewModels的新UI元素，所有这些都存在于View层中。

但是......有许多模式围绕MVVM发展以支持这一点。通常，这是使用服务或控制器来处理视图操作，检查您选择的MVVM库是否支持显示新视图的方法。

最后有一件事让我感到困惑，当你需要同时执行操作并更改视图时会发生什么。通常，您将UI对象（例如按钮）绑定到ViewModel级别命令以执行操作，并依赖绑定来更新显示新值的UI控件。由于ViewModel不应该知道View，因此任何更改UI的操作都必须仅在View中进行。这意味着您无法绑定到ViewModel命令。幸运的是，您可以在视图级别创建一个命令，该命令委派给视图模型级别操作并更改UI。

（嗯......回头看，不确定这会回答这个问题，但这可能有助于澄清你的想法）

这是使用MVVM设计模式创建新窗口的最佳方式

2 个答案: