Silverlight Application是客户端程序，没有也无法访问服务端的web.config，它自己也不允许添加.config文件，加上Silverilght 3.0之后，原来ASP.NET 2.0中的Silveright控件也被去掉了，要读取web.config就又更困难了一些。
不过如果仔细分析一下的话，可以发现Silverlight App是由一个Web Application来host的，而那个Web Application是可以方便地配置的，于是，可以考虑由网站来把配置传给Silverlight，宿主Silverlight的Page文件中会有这样一段代码：
<param name="source" value="ClIEntBin/GetWebConfig.xap"/><param name="onError" value="onSilverlightError" /><param name="background" value="white" /><param name="minRuntimeVersion" value="4.0.50826.0" /><param name="autoUpgrade" value="true" />
可以看到这里有很多关于Silverlight的参数，我们可以从这段代码下手，在这里为其添加一个新的参数：
<param name="InitParams" value="127.0.0.1" />
可以看到其中有一个param标签的name为InitParams，其值可以在App.xaml.cs中的Application_Startup事件处理方法中，使用传入StartupEventArgs参数的InitParams属性取得，类型为IDictionary<string,string>。下面来看一下具体的方法：
1. 首先，我们需要在Page文件中加入一个literal控件，以便能够动态地将<param name="InitParams" value="" />赋到Page中，但是在Visual Studio 2010里，默认为我们创建的ASPX页面没有.cs文件，需要我们创建一个新的ASPX页面，把原先<HTML></HTML>当中的内容copy过来，并加上literal控件，如下方代码所示：
<%@ Page Language="C#" autoEventWireup="true" CodeBehind="HostPage.aspx.cs" inherits="GetWebConfig.Web.HostPage" %><!DOCTYPE HTML PUBliC "-//W3C//DTD xhtml 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-Transitional.dtd"><HTML xmlns="http://www.w3.org/1999/xhtml"><head runat="server"> <Title>GetWebConfig</Title> <style type="text/CSS"> HTML,body { height: 100%; overflow: auto; } body { padding: 0; margin: 0; } #silverlightControlHost { height: 100%; text-align:center; } </style> <script type="text/JavaScript" src="Silverlight.Js"></script> <script type="text/JavaScript"> function onSilverlightError(sender,args) { var appSource = ""; if (sender != null && sender != 0) { appSource = sender.getHost().source; } var errorType = args.ErrorType; var IErrorCode = args.ErrorCode; if (errorType == "ImageError" || errorType == "MediaError") { return; } var errMsg = "Unhandled Error in Silverlight Application " + appSource + "\n"; errMsg += "Code: " + IErrorCode + " \n"; errMsg += "category: " + errorType + " \n"; errMsg += "Message: " + args.ErrorMessage + " \n"; if (errorType == "ParserError") { errMsg += "file: " + args.xamlfile + " \n"; errMsg += "line: " + args.lineNumber + " \n"; errMsg += "position: " + args.charposition + " \n"; } else if (errorType == "RuntimeError") { if (args.lineNumber != 0) { errMsg += "line: " + args.lineNumber + " \n"; errMsg += "position: " + args.charposition + " \n"; } errMsg += "Methodname: " + args.methodname + " \n"; } throw new Error(errMsg); } </script></head><body> <form ID="form1" runat="server"> <div ID="silverlightControlHost"> <object data="data:application/x-silverlight-2," type="application/x-silverlight-2" wIDth="100%" height="100%"> <param name="source" value="ClIEntBin/GetWebConfig.xap"/> <param name="onError" value="onSilverlightError" /> <param name="background" value="white" /> <param name="minRuntimeVersion" value="4.0.50826.0" /> <param name="autoUpgrade" value="true" /> <asp:literal ID="litinitParams" runat="server" /> <a href="http://go.microsoft.com/fwlink/?linkID=149156&v=4.0.50826.0" > <img src="http://go.microsoft.com/fwlink/?linkID=161376" alt="Get Microsoft Silverlight" /> </a> </object><iframe ID="_sl_historyFrame" ></iframe></div> </form></body></HTML> 2. 接下来，我们要在这个页面的后台.cs文件中读取web.config的内容，并且把它赋给literal控件：
using System;using System.Collections.Generic;using System.linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.Collections.Specialized;using System.Web.Configuration;using System.Text; namespace SL_ReadConfigfile.Web{ public partial class SL_ReadConfigfile : System.Web.UI.Page { private string _seperator = ","; protected voID Page_Load( object sender,EventArgs e ) { Response.Cache.SetCacheability( httpCacheability.NoCache ); WriteInitParams(); } private voID WriteInitParams() { nameValueCollection appSettings = WebConfigurationManager.AppSettings; StringBuilder stringBuilder = new StringBuilder(); stringBuilder.Append( "<param name=\"InitParams\" value=\"" ); string paramContent = string.Empty; for( int i = 0 ; i < appSettings.Count ; i++ ) { if( paramContent.Length > 0 ) { paramContent += _seperator; } paramContent += string.Format( "{0}={1}",appSettings.GetKey( i ),appSettings[ i ] ); } stringBuilder.Append(paramContent ); stringBuilder.Append( "\" />" ); this.litinitParams.Text = stringBuilder.ToString(); } } } 3. 在App.xaml.cs中的Application_Startup事件处理方法中，使用传入StartupEventArgs参数的InitParams属性取得，类型为IDictionary<string,string>：
using System;using System.Collections.Generic;using System.windows; namespace SL_ReadConfigfile{ public partial class App : Application { private IDictionary<string,string> _configurations; public IDictionary<string,string> Configurations { get { return _configurations; } } public App() { this.Startup += this.Application_Startup; this.Exit += this.Application_Exit; this.UnhandledException += this.Application_UnhandledException; InitializeComponent(); } private voID Application_Startup( object sender,StartupEventArgs e ) { _configurations = e.InitParams; this.RootVisual = new MainPage(); } private voID Application_Exit( object sender,EventArgs e ) { } private voID Application_UnhandledException( object sender,ApplicationUnhandledExceptionEventArgs e ) { if( !System.Diagnostics.DeBUGger.IsAttached ) { e.Handled = true; Deployment.Current.dispatcher.BeginInvoke( delegate { ReportErrorTodoM( e ); } ); } } private voID ReportErrorTodoM( ApplicationUnhandledExceptionEventArgs e ) { try { string errorMsg = e.ExceptionObject.Message + e.ExceptionObject.StackTrace; errorMsg = errorMsg.Replace( '"','\'' ).Replace( "\r\n",@"\n" ); System.windows.browser.HTMLPage.Window.Eval( "throw new Error(\"Unhandled Error in Silverlight Application " + errorMsg + "\");" ); } catch( Exception ) { } } }} 4. 最后就是在Silverlight页面当中获取InitParams的值并显示到页面上：
<UserControl xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk" x:Class="SL_ReadConfigfile.MainPage" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/Expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" d:DesignWIDth="800" d:DesignHeight="600" WIDth="auto" Height="auto" xmlns:toolkit="http://schemas.microsoft.com/winfx/2006/xaml/presentation/toolkit"> <GrID x:name="LayoutRoot" Background="transparent"> <GrID.RowDeFinitions> <RowDeFinition Height="50"></RowDeFinition> <RowDeFinition></RowDeFinition> <RowDeFinition Height="30"></RowDeFinition> </GrID.RowDeFinitions> <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center" FontSize="24">Silverlight Reads web.config Demo</TextBlock> <sdk:DataGrID GrID.Row="1" name="dgdConfigurations"> </sdk:DataGrID> <StackPanel OrIEntation="Horizontal" GrID.Row="2" HorizontalAlignment="Center"> <@R_404_5554@ name="btnShowEntry" WIDth="200" margin="10,0" Click="btnShowEntry_Click"> <StackPanel OrIEntation="Horizontal"> <TextBlock VerticalAlignment="Center">Read number</TextBlock> <toolkit:Numericupdown name="numericupdown" margin="5,0" DecimalPlaces="0"/> <TextBlock VerticalAlignment="Center">entry</TextBlock></StackPanel> </@R_404_5554@> <@R_404_5554@ name="btnBindConfig" WIDth="200" margin="10,0" Click="btnBindConfig_Click">Binding Configurations</@R_404_5554@> </StackPanel> </GrID></UserControl>
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; namespace SL_ReadConfigfile{ public partial class MainPage : UserControl { private IDictionary<string,string> _configurations; public MainPage() { InitializeComponent(); _configurations = ( Application.Current as App ).Configurations; if( _configurations.Count > 0 ) { numericupdown.Minimum = 1; numericupdown.Maximum = _configurations.Count; } } private voID btnBindConfig_Click( object sender,RoutedEventArgs e ) { this.dgdConfigurations.ItemsSource = _configurations; } private voID btnShowEntry_Click( object sender,RoutedEventArgs e ) { string entryContent = string.Format( "{0} = {1}",_configurations.ElementAt( ( int ) numericupdown.Value - 1 ).Key,_configurations.ElementAt( ( int ) numericupdown.Value - 1 ).Value ); MessageBox.Show( entryContent ); } }}
5. 我们已经可以读取到web.config里面的值了，但是，要注意的是，在ASPX页面当中InitParams会以明文显示在Source Code当中，如果是数据库连接串或是其他需要加密的信息，请自己开发加密算法来解决这一问题，下一篇我会介绍如何加密InitParams中的值。
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