首先你需要下载Microsoft Web Platform Installer 2.0 Beta

下载完后启动安装包，它会去获取最新的网络安装包信息

我惊喜的发现Silverlight 3 Tools for Visual Studio 2008 SP1 Beta已经可以下载了

其详细信息如下图所示，并和Silverlight 2 Tools比较，发现Silverlight 3 Tools的大小反而小了很多，压缩了1倍多

Silverlight 3 Tools的版本号由Silverlight 2 Tools的9.0.30729.146提升到了9.0.30729.463

此外我们还从上面看到了ASP.NET MVC 1.0正式版

这两个Web组件估计都是明天在MIX2009上才发布的

不过不小心通过Microsoft Web Platform Installer 2.0 Beta泄露出来了

但是目前的问题是简体中文版的VS2008 SP1不能安装（亲身测试过）

Silverlight 3的文档也已经提供了下载

Silverlight 3 Tools For Visual Studio Beta也可以从这里下载

在英文版的VS2008 sp1上安装过后，Silverlight 3 Runtime版本号是3.0.40307.0

Silverlight 3包含了三个工程Silverlight Application，Silverlight Navigation Application（这个是最新的），Silverlight Class Library

创建网站的类型依托现在依托在ASP.NET网站

ToolBox的控件也增加了很多，包括所有的2含有的控件+Silverlight Toolkit包+少量新控件（比如ErrorSummary等）

Silverlight 3 Beta和Silverlight 2之间的兼容性做的不错，看下下面的 Breaking Change文档就知道了

Ensuring That Your Silverlight 2 Applications Work with the Silverlight 3 Beta Release

Introduction

This topic discusses the changes made to the Silverlight runtime andSilverlight tools between the Microsoft Silverlight 2 and Silverlight 3Beta. The changes discussed in this article are focused on changes thatmight cause your older Silverlight-based applications to now fail orbehave differently, not on new features/enhancements for this release.

Note   Corrections/Additions to this document (if any) are listed here.

Contents:

· OpenFileDialog.ShowDialog() can now only be opened from a user initiated event

· HyperlinkButton now navigates the entire window and not just the IFRAME that Silverlight is in

· Mouse events inside a Popup now give positions relative to the pop-up not the entire application

· ReadOnlyObservableCollection moved from System.Windows.Controls.Data.dll to System.Windows.dll

OpenFileDialog.ShowDialog() can now only be opened from a user initiated event

Who Is Affected: All applications.

Summary

For security reasons, OpenFileDialog.ShowDialog() may only be calledduring a user initiated event (MouseLeftButtonDown/Up and KeyDown/Up)or derived user event like clicking a button, checking a checkbox, etc.This brings Silverlight into line with how the other major browsers andplug-ins behave.

HyperlinkButton now navigates the entire window and not just the IFRAME that Silverlight is in

Who Is Affected: Silverlight 2 applications recompiled for Silverlight 3 Beta.

Summary

In Silverlight 2, HyperlinkButton behaved inconsistently acrossbrowsers. In Internet Explorer, HyperlinkButton will navigate theentire browser not just the current IFrame.

In other browsers, HyperlinkButton navigates only the currentIFrame, which is consistent with HTML behavior. In Silverlight 3 Beta,we've changed the behavior inside Internet Explorer to match thebehavior in other browsers.

Mouse events inside a Popup now give positions relative to the pop-up not the entire application

Who Is Affected: Silverlight 2 applications recompiled for Silverlight 3 Beta.

Summary

Suppose you have an element inside a pop-up that listens to mouse events:

[xaml]

<Popup>

<Border Name="border" MouseLeftButtonDown="OnMouseLeftButtonDown"/>

</Popup>

[c#]

void OnMouseLeftButtonDown(object sender, MouseButtonEventArgs e)

{

… e.GetPosition(border) ...

}

In Silverlight 2, the coordinates fromMouseButtonEventArgs.GetPosition will be relative to the entireSilverlight plug-in, even though the application asked for coordinatesrelative to the border control (the parameter to GetPosition issupposed to indicate the frame of reference). This has been fixed inSilverlight 3 Beta.

ReadOnlyObservableCollection moved from System.Windows.Controls.Data.dll to System.Windows.dll

Who Is Affected: Silverlight 2 applications recompiled for Silverlight 3 Beta.

Summary

This class has been moved into System.Windows.dll so that other APIsin System.Windows.dll can use it. In order to minimize download sizeimpact we've removed some uncommonly used methods.

Note that this will not affect applications compiled for Silverlight2. If you use ReadOnlyObservableCollection in Silverlight 2, your .xapfile will contain a copy of System.Windows.Controls.Data.dll. WhenSilverlight 3 Beta runs your .xap, it will use the .xap's copy ofSystem.Windows.Controls.Data.dll and that version ofReadOnlyObservableCollection, not the version that ships in theSystem.Windows.dll of Silverlight 3 Beta.