MVVM Silverlight 和页面导航 [英] MVVM Silverlight and page navigation

问题描述

我刚开始使用 Silverlight 和 MVVM 模型.当执行页面导航并将参数从一个页面发送到另一个页面时，.. 使用查询字符串是最被接受的方法吗?

I'm just starting out with Silverlight and also with the MVVM model. When performing page navigation and sending arguments from one page to another, .. is the use of querystring the most accepted method?

在执行页面导航时应该如何传递参数似乎是一个很大的困惑.至少我在各种网络资源上找到了几个关于此的主题，但似乎没有人同意最佳实践"方法.

It seems to be a big confusion on how passing arguments while performing page navigation should be performed. At least I find several topics about this on various web resources, but no one seems to agree upon a "best practice" method.

推荐答案

注意:以下在 NavigationContext 中使用查询字符串的解决方案适用于浏览器内外.

NOTE: The below solution of using query strings in the NavigationContext works for both in and out of browser.

您通常将 UriMapper 设置为如下所示:

You normally set your UriMapper something like this:

           <navigation:Frame Source="/Home" >
                <navigation:Frame.UriMapper>
                    <uriMapper:UriMapper>
                        <uriMapper:UriMapping Uri="" 
                                   MappedUri="/Views/Home.xaml"/>
                        <uriMapper:UriMapping Uri="/{pageName}/{key}" 
                                   MappedUri="/Views/{pageName}.xaml?entityGuid={key}"/>
                        <uriMapper:UriMapping Uri="/{pageName}" 
                                   MappedUri="/Views/{pageName}.xaml"/>
                    </uriMapper:UriMapper>
                </navigation:Frame.UriMapper>
            </navigation:Frame>

然后为了让 NavigationContext 进入视图模型，你可以像这样向你的视图添加一个助手:

And then to get the NavigationContext into the view model, you add a helper to your View like so:

<navigation:Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                 xmlns:helpers="clr-namespace:MyApp.Helpers"
                 xmlns:navigation="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Navigation"
                 DataContext="{Binding Path=Entity, Source={StaticResource Locator}}"
                 helpers:Navigator.Source="{Binding}">

然后你有一个像这样的附加属性助手(我从别人那里修改了这个，虽然我忘了是谁):

And then you have an attached property helper like so (I modified this from someone else, though I forgot who):

using System.Windows;
using System.Windows.Controls;

namespace MyApp.Helpers
{

    public interface INavigable
    {
        System.Windows.Navigation.NavigationService NavigationService { get; set; }
        System.Windows.Navigation.NavigationContext NavigationContext { get; set; }
    }


    public static class Navigator
    {
        public static INavigable GetSource(DependencyObject obj)
        {
            return (INavigable)obj.GetValue(SourceProperty);
        }

        public static void SetSource(DependencyObject obj, INavigable value)
        {
            obj.SetValue(SourceProperty, value);
        }

        public static readonly DependencyProperty SourceProperty =
             DependencyProperty.RegisterAttached("Source", typeof(INavigable), typeof(Navigator), new PropertyMetadata(OnSourceChanged));

        private static void OnSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            Page page = (Page)d;

            page.Loaded += PageLoaded;
        }

        private static void PageLoaded(object sender, RoutedEventArgs e)
        {
            Page page = (Page)sender;

            INavigable navSource = GetSource(page);

            if (navSource != null)
            {
                navSource.NavigationService = page.NavigationService;
                navSource.NavigationContext = page.NavigationContext;
            }
        }
    }
}

然后将以下内容添加到您的 ViewModel:

And then add the following to your ViewModel:

    private NavigationContext _NavigationContext;
    public NavigationContext NavigationContext {
        get { return _NavigationContext; }
        set {
            if (_NavigationContext == value)
                return;
            _NavigationContext = value;
            RaisePropertyChanged("NavigationContext");
        }
    }
    protected override void RaisePropertyChanged(string propertyName) {
        base.RaisePropertyChanged(propertyName);

        switch (propertyName) {
            case "NavigationContext":
                if (NavigationContext.QueryString.ContainsKey("entityGuid")) {
                    if (NavigationContext.QueryString["entityGuid"].Equals("new", StringComparison.InvariantCultureIgnoreCase)) {
                        LoadNewEntity();  // your 'new' logic
                    } else {
                        this.EntityGuid = new Guid(NavigationContext.QueryString["entityGuid"]);
                        LoadExistingEntity(EntityGuid);  // your 'existing' logic
                    }
                }
                break;
        }
    }

这篇关于MVVM Silverlight 和页面导航的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！