网络编程：XML、SOAP、JSON、RSS与Socket的综合应用

# 网络编程：XML、SOAP、JSON、RSS与Socket的综合应用 ## 1. XML-RPC与Flickr图像搜索 当通过XML - RPC调用Flickr图像搜索时，会得到一个XML - RPC响应。若要获取之前使用的照片信息，需对消息调用`HttpUtility.HtmlDecode()`，再使用LINQ to XML过滤出`<photo>`元素。完整代码可参考相关示例。 使用`XDocument`和LINQ to XML可进行XML的读取和创建，这些技术在处理基于XML的Web服务时非常有用，也适用于其他XML处理场景。`XDocument`和`XElement`类有很多方法，可轻松修改XML文档，如`Add()`、`AddAfterSelf()`等。 ## 2. 返回SOAP数据的服务 Silverlight能与.NET Web服务无缝协作，这些服务发送SOAP编码的数据。SOAP是XML的一种形式，理论上可使用Silverlight的XML处理（如`XDocument`类）创建请求消息和解析响应消息，但在Visual Studio中添加服务引用更为简便。此技术适用于任何基于SOAP的Web服务，Silverlight无法区分服务是否由.NET构建。添加Web引用时，Visual Studio会创建所需的代理类，包含异步方法和事件。 ## 3. 返回JSON数据的服务 ### 3.1 JSON概述 JavaScript对象表示法（JSON）是一种对象表示语法，有时作为XML的轻量级替代方案。当使用返回JSON数据且无SOAP替代方案的Web服务时，需使用JSON序列化器。Silverlight提供两种解析JSON数据的方式：使用JSON反序列化器或LINQ to JSON。在处理JSON数据前，需添加三个程序集引用：`System.Runtime.Serialization.dll`、`System.ServiceModel.dll`和`System.ServiceModel.Web.dll`。 ### 3.2 反序列化JSON示例 以Yahoo!的图像搜索服务为例，其返回的JSON数据如下： ```json {"ResultSet":{ "totalResultsAvailable":"957841", "totalResultsReturned":10, "firstResultPosition":1, "Result":[ { "Title":"tree_frog.jpg", "Summary":"Red - Eyed Tree Frog", "Url":"https:\/\/2.zoppoz.workers.dev:443\/http\/www.thekidscollege.com\/images\/animals\/redeyetree_frog.jpg", ... }, { "Title":"tree_frog_large - thumb.jpg", "Summary":"Before I came back in though I got another shot of the frog.", "Url":"https:\/\/2.zoppoz.workers.dev:443\/http\/www.silveriafamily.com\/blog\/john\/treefrog.jpg", ... } ] }} ``` 为对这些数据进行建模，需创建相应的类： ```vb Public Class SearchResults Public ResultSet As SearchResultSet End Class Public Class SearchResultSet Private _totalResultsAvailable As Integer Public Property totalResultsAvailable() As Integer ... End Property Private _totalResultsReturned As Integer Public Property totalResultsReturned() As Integer ... End Property Private _result As SearchResult() Public Property Result() As SearchResult() ... End Property End Class Public Class SearchResult Private _title As String Public Property Title() As String ... End Property Private _summary As String Public Property Summary() As String ... End Property Private _url As String Public Property Url() As String ... End Property End Class ``` 反序列化步骤如下： 1. 创建`DataContractJsonSerializer`实例： ```vb Dim serializer As New DataContractJsonSerializer(GetType(SearchResults)) ``` 2. 使用`ReadObject()`反序列化JSON数据： ```vb Dim results As SearchResults = CType(serializer.ReadObject(jsonData), SearchResults) ``` 以下是一个搜索图像的Silverlight页面代码示例： ```vb Private Sub cmdGetData_Click(ByVal sender As Object, ByVal e As RoutedEventArgs) Dim client As New WebClient() Dim address As New Uri( _ "http://search.yahooapis.com/ImageSearchService/V1/imageSearch?" & _ "appid=YahooDemo&query=" & HttpUtility.UrlEncode(txtSearchKeyword.Text) & _ "&output=json") AddHandler client.OpenReadCompleted, AddressOf client_OpenReadCompleted client.OpenReadAsync(address) End Sub Private Sub client_OpenReadCompleted(ByVal sender As Object, _ ByVal e As OpenReadCompletedEventArgs) Dim serializer As New DataContractJsonSerializer(GetType(SearchRes ```