Silverlight：利用异步加载Xap实现自定义loading效果

               虽然在silverlight中微软自带了加载了silverlight项目时加载进度，但是如何自己定义加载精度条呢？本篇学习了如何自定义自己的加载进度条！本篇参考了http://www.cnblogs.com/yjmyzz/archive/2009/12/22/1629947.html这篇文章！

（一）关键点:
1.利用WebClient的DownloadProgressChanged事件更新下载进度
2.下载完成后，分析Xap包的程序集Assembly信息

3.利用Assembly反射还原对象并加载到当前页中。 

（二）好处:
1.可以先定义一个简单的加载动画，吸引用户注意，避免长时间的无聊等待，改善用户体验。
2.实现按需加载，避免一次性下载过多内容。

3.在一定程度上，增加了破解难度，有助于代码保密。

（三）项目实现：

（1）项目结构如下

（2）项目说明:

   LoadXap使来显示加载的进度条的，而MainXap是我们要加载的Xap包，里面的MainPage中包含一个Image空间（显示一张图片）,当进度条加载完毕后将,MainXap中的MainPage加到LoadXap中MainPage中。 这样就是实现了加载异步加载xap中的Page或者用户空间了！

  值得注意的地方：在LoadXap项目中应添加MainXap.dll的引用，不然在 Assembly assembly = GetAssemblyFromXap(e.Result, "MainXap.dll");时会找不到该MainXap.dll程序集的。会报错的。

（3）项目LoadXap中主要代码

       MainPage.xaml中的代码：

 <Grid x:Name="LayoutRoot">
        <StackPanel VerticalAlignment="Center" HorizontalAlignment="Center" Orientation="Horizontal">
            <ProgressBar Height="15" VerticalAlignment="Center" HorizontalAlignment="Center" Width="200" x:Name="pb1" Value="0"/>
            <TextBlock x:Name="txtLoad" Text="0%" Margin="5,0,0,0"></TextBlock>
        </StackPanel>
    </Grid>

      MainPage.xaml.cs的代码：

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
//添加命名空间
using System.Windows.Browser;
using System.IO;
using System.Text.RegularExpressions;
using System.Reflection;
using System.Xml;
using System.Windows.Resources;

namespace LoadXap
{
    public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();
            this.Loaded += new RoutedEventHandler(MainPage_Loaded);
        }

        void MainPage_Loaded(object sender, RoutedEventArgs e)
        {
            WebClient wc = new WebClient();
            wc.OpenReadCompleted += new OpenReadCompletedEventHandler(wc_OpenReadCompleted);
            wc.DownloadProgressChanged += new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged);
            Uri xapUri = new Uri(HtmlPage.Document.DocumentUri, "ClientBin/MainXap.xap");            
            wc.OpenReadAsync(xapUri);
        }

        void wc_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
        {
            this.txtLoad.Text = e.ProgressPercentage.ToString() + "%";
            this.pb1.Value = (double)e.ProgressPercentage;
        }

        void wc_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
        {
            Assembly assembly = GetAssemblyFromXap(e.Result, "MainXap.dll");
            UIElement element = assembly.CreateInstance("MainXap.MainPage") as UIElement;
            this.LayoutRoot.Children.Add(element);
        }


        /// <summary>
        /// 从XAP包中返回程序集信息
        /// </summary>
        /// <param name="packageStream"></param>
        /// <param name="assemblyName"></param>
        /// <returns></returns>
        private Assembly GetAssemblyFromXap(Stream packageStream, String assemblyName)
        {
            Stream stream = Application.GetResourceStream(new StreamResourceInfo(packageStream, null), new Uri("AppManifest.xaml", UriKind.Relative)).Stream;
            Assembly asm = null;
            XmlReader xmlReader = XmlReader.Create(stream);
            xmlReader.MoveToContent();
            if (xmlReader.ReadToFollowing("Deployment.Parts"))
            {
                string str = xmlReader.ReadInnerXml();
                Regex reg = new Regex("x:Name=\"(.+?)\"");
                Match match = reg.Match(str);
                string sName = "";
                if (match.Groups.Count == 2)
                {
                    sName = match.Groups[1].Value;
                }
                reg = new Regex("Source=\"(.+?)\"");
                match = reg.Match(str);
                string sSource = "";
                if (match.Groups.Count == 2)
                {
                    sSource = match.Groups[1].Value;
                }
                AssemblyPart assemblyPart = new AssemblyPart();
                StreamResourceInfo streamInfo = App.GetResourceStream(new StreamResourceInfo(packageStream, "application/binary"), new Uri(sSource, UriKind.Relative));
                if (sSource == assemblyName)
                {
                    asm = assemblyPart.Load(streamInfo.Stream);
                }
            }
            return asm;
        }

    }
}

源代码下载