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" style="text-decoration:none">
<img src="http://go.microsoft.com/fwlink/?LinkId=161376" alt="Get Microsoft Silverlight" style="border-style:none"/>
</a>
</object><iframe id="_sl_historyFrame" style="visibility:hidden;height:0px;0px;border:0px"></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">
<Button 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>
</Button>
<Button Name="btnBindConfig" Width="200" Margin="10,0" Click="btnBindConfig_Click">Binding Configurations</Button>
</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。