Silverlight：利用异步加载Xap实现自定义loading效果

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。

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。

Xaml ：

代码using System;
using System.IO;
using System.Net;
using System.Reflection;
using System.Text.RegularExpressions;
using System.Windows;
using System.Windows.Browser;
using System.Windows.Controls;
using System.Windows.Resources;
using System.Xml;

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;
}
}
}
演示效果：http://images.24city.com/jimmy/loadXap/