Using Returned XML

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YDN Silverlight Developer Center

Silverlight: Using Returned XML

Overview
Using the XmlReader Class
Using the XmlSerializer Class
Using XLINQ
Using RSS and Atom Feeds
Further Reading

Overview

Silverlight provides a rich toolset to work with XML data with the different options suited for different tasks. This page covers the most common ways to work with XML data. For simplicity, all of the examples below use Atom XML data fetched from http://api.flickr.com/services/feeds/photos_public.gne. However, when working with Atom and RSS feeds it is usually easier to use the Silverlight feed classes. See Using RSS and Atom Feeds below.

Using the `XmlReader` Class

The XmlReader class provides fast read- and forward-only access to data and is well suited for iterating over an XML document. It can read data from a stream or it can be passed a URI to a file that is located within the application's XAP.

Example

The following example shows how to take an existing stream and output the content of the text nodes in the document.

// using System.Xml;
        private void IterateData(System.IO.Stream stream)
        {
            StringBuilder output = new StringBuilder();

using (var reader = XmlReader.Create(stream))
            {
                // Move to the start of the actual content
                reader.MoveToContent();

// Read until the end of the document
                while (reader.Read())
                {
                    // Check node type
                    switch (reader.NodeType)
                    {
                        case XmlNodeType.Element:
                            if (reader.IsEmptyElement == false)
                            {
                                output.Append(System.Environment.NewLine + reader.Name + " = ");
                            }
                            break;
                        case XmlNodeType.Text:
                            output.Append(reader.Value);
                            break;
                        case XmlNodeType.EndElement:
                            output.Append(System.Environment.NewLine);
                            break;
                    }  // switch (reader.NodeType)
                }  // while (reader.Read())
            }  // using

// Output the result
            Debug.WriteLine(output.ToString());
        }

Visual Basic Example

' Imports System.Xml
    Private Sub IterateData(ByVal stream As Stream)

Dim output As New StringBuilder

Using reader As XmlReader = XmlReader.Create(stream)

' Move to the start of the actual content
            reader.MoveToContent()

' Read until the end of the document
            Do While reader.Read

' Check node type
                Select Case reader.NodeType
                    Case XmlNodeType.Element
                        If Not reader.IsEmptyElement Then
                            output.Append((Environment.NewLine & reader.Name & " = "))
                        End If
                        Exit Select
                    Case XmlNodeType.Text
                        output.Append(reader.Value)
                        Exit Select
                    Case XmlNodeType.EndElement
                        output.Append(Environment.NewLine)
                        Exit Select
                End Select
            Loop

End Using

Debug.WriteLine(output.ToString)
    End Sub

Using the `XmlSerializer` Class

For well-known data structures, such as business objects, it is often necessary to read external data and import it into internal strongly typed objects. The XmlSerializer class lets you easily deserialize XML into managed objects. The downside of using XmlSerializer is the requirement to reference the external System.Xml.Serialization.dll assembly which will increase your XAP size by approximately 150kB.

Example

The following example shows how to take an existing stream and deserialize the data into strongly-typed objects. The abbreviated data classes are shown after the method.

C# Example

Visual Basic Example

<XmlRoot(ElementName:="feed", Namespace:="http://www.w3.org/2005/Atom")> _
Public Class AtomFeed

Private _title As String
    Private _id As String
    Private _icon As String
    Private _entries As List(Of FeedEntry)

<XmlElement(ElementName:="title")> _
    Public Property Title() As String
        Get
            Return _title
        End Get
        Set(ByVal value As String)
            _title = value
        End Set
    End Property

<XmlElement(ElementName:="id")> _
    Public Property Id() As String
        Get
            Return _id
        End Get
        Set(ByVal value As String)
            _id = value
        End Set
    End Property

<XmlElement(ElementName:="icon")> _
    Public Property Icon() As String
        Get
            Return _icon
        End Get
        Set(ByVal value As String)
            _icon = value
        End Set
    End Property

<XmlElement(ElementName:="entry")> _
    Public Property Entries() As List(Of FeedEntry)
        Get
            Return _entries
        End Get
        Set(ByVal value As List(Of FeedEntry))
            _entries = value
        End Set
    End Property

End Class

<XmlRoot(ElementName:="entry", Namespace:="http://www.w3.org/2005/Atom")> _
Public Class FeedEntry

Private _title As String
    Private _content As String

<XmlElement(ElementName:="content")> _
    Public Property Content() As String
        Get
            Return _content
        End Get
        Set(ByVal value As String)
            _content = value
        End Set
    End Property

End Class

Using `XLINQ`

Link to XML provides an easier read/write interface than the traditional XML Document Object Model. Integration with LINQ allows you to write queries and modify the contents of the document. The downside of using XLINQ is the requirement to reference the external System.Xml.Linq.dll assembly which will increase your XAP size by approximately 56kB.

Example

The following example shows how to take an existing stream, sort the results based on an element, and output selected data.

C# Example

// using System.Linq;
        // using System.Xml;
        // using System.Xml.Linq;
        private void QueryData(System.IO.Stream stream)
        {
            var reader = XmlReader.Create(stream);
            var document = XDocument.Load(reader);
            var output = new StringBuilder();

// Use the Atom namespace
            XNamespace atom = "http://www.w3.org/2005/Atom";

// Get all Atom entries sorted by author
            var entries =
                from entry in document.Descendants(atom + "entry")
                let author = (string)entry.Element(atom + "author").Element(atom + "name")
                orderby author
                select entry;

// Iterate through the results and output some information
            foreach (var entry in entries)
            {
                output.AppendLine("Title: " + (string)entry.Element(atom + "title"));
                output.AppendLine("Author: " 
                    + (string)entry.Element(atom + "author").Element(atom + "name"));
            }  // foreach

// Output the result
            Debug.WriteLine(output.ToString());
        }

Visual Basic Example

Using RSS and Atom Feeds

Silverlight provides support for RSS and Atom feeds in the System.ServiceModel.Syndication namespace which makes it very easy to work with these common data structures. The downside of using the feed support is the requirement to reference the external System.ServiceModel.Syndication.dll assembly which will increase your XAP size by approximately 53kB.

Example

The following example shows how to take an existing stream and output the entry titles using feed support.

Silverlight: Using Returned XML

Overview

Using the XmlReader Class

Example

Visual Basic Example

Using the XmlSerializer Class

Example

C# Example

Visual Basic Example

Using XLINQ

Example

C# Example

Visual Basic Example

Using RSS and Atom Feeds

Example

C# Example

Visual Basic Example

Further Reading

Using the `XmlReader` Class

Using the `XmlSerializer` Class

Using `XLINQ`