Using Returned JSON

Silverlight: Using Returned JSON

Overview
Using the DataContractJsonSerializer Class
Using the JsonObject Class
Further Reading

Overview

Using JSON formatted data instead of XML can be an advantage when optimum download speed is desired and the data doesn't require the use of XML attributes. While GZip compression often minimizes the size differences between XML and JSON, it may not be sufficient due to the overhead caused by the XML schema in use. In other cases you may need to interact with JavaScript and interoperability will be easier using JSON.

The example below use JSON formatted data fetched from http://api.flickr.com/services/feeds/photos_public.gne?format=json&nojsoncallback=1.

Using the `DataContractJsonSerializer` Class

Similar to the XmlSerializer class, DataContractJsonSerializer maps data from a JSON file into strongly managed objects.

Example

The following classes are used to store the received data in strongly-typed objects. Note the use of the Name property on the DataMember attribute to rename the data into the correct naming convention used in .NET.

C# Example

// using System;
    // using System.Collections.Generic;
    // using System.Runtime.Serialization;
    [DataContract]
    public class Photos
    {
        [DataMember(Name="title")]
        public string Title { get; set; }

[DataMember(Name = "link")]
        public Uri Link { get; set; }

[DataMember(Name = "description")]
        public string Description { get; set; }

[DataMember(Name = "modified")]
        public string Modified { get; set; }

[DataMember(Name = "generator")]
        public string Generator { get; set; }

[DataMember(Name = "items")]
        public List<Photo> Items { get; set; }
    }

[DataContract]
    public class Photo
    {
        [DataMember(Name = "title")]
        public string Title { get; set; }

[DataMember(Name = "link")]
        public Uri Link { get; set; }

[DataMember(Name = "media")]
        public Media Media { get; set; }

[DataMember(Name = "data_taken")]
        public string DateTaken { get; set; }

[DataMember(Name = "description")]
        public string Description { get; set; }

[DataMember(Name = "published")]
        public DateTime Published { get; set; }

[DataMember(Name = "author")]
        public string Author { get; set; }

[DataMember(Name = "authorid")]
        public string AuthorId { get; set; }

[DataMember(Name = "tags")]
        public string Tags { get; set; }
    }

[DataContract]
    public class Media
    {
        [DataMember(Name = "m")]
        public Uri Source { get; set; }
    }

Visual Basic Example

<DataContract()> _
Public Class Photos

Private _title As String
    Private _link As Uri
    Private _description As String
    Private _modified As String
    Private _generator As String
    Private _items As List(Of Photo)

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

<DataMember(Name:="link")> _
    Public Property Link() As Uri
        Get
            Return _link
        End Get
        Set(ByVal value As Uri)
            _link = value
        End Set
    End Property

<DataMember(Name:="description")> _
    Public Property Description() As String
        Get
            Return _description
        End Get
        Set(ByVal value As String)
            _description = value
        End Set
    End Property

<DataMember(Name:="modified")> _
    Public Property Modified() As String
        Get
            Return _modified
        End Get
        Set(ByVal value As String)
            _modified = value
        End Set
    End Property

<DataMember(Name:="generator")> _
    Public Property Generator() As String
        Get
            Return _generator
        End Get
        Set(ByVal value As String)
            _generator = value
        End Set
    End Property

<DataMember(Name:="items")> _
    Public Property Items() As List(Of Photo)
        Get
            Return _items
        End Get
        Set(ByVal value As List(Of Photo))
            _items = value
        End Set
    End Property
End Class

<DataContract()> _
Public Class Photo

Private _title As String
    Private _link As Uri
    Private _media As Media
    Private _dateTaken As String
    Private _description As String
    Private _published As String
    Private _author As String
    Private _authorId As String
    Private _tags As String

<DataMember(Name:="media")> _
    Public Property Media() As Media
        Get
            Return _media
        End Get
        Set(ByVal value As Media)
            _media = value
        End Set
    End Property

<DataMember(Name:="date_taken")> _
    Public Property DateTaken() As String
        Get
            Return _dateTaken
        End Get
        Set(ByVal value As String)
            _dateTaken = value
        End Set
    End Property

<DataMember(Name:="published")> _
    Public Property Published() As String
        Get
            Return _published
        End Get
        Set(ByVal value As String)
            _published = value
        End Set
    End Property

<DataMember(Name:="author")> _
    Public Property Author() As String
        Get
            Return _author
        End Get
        Set(ByVal value As String)
            _author = value
        End Set
    End Property

<DataMember(Name:="authorid")> _
    Public Property AuthorId() As String
        Get
            Return _authorId
        End Get
        Set(ByVal value As String)
            _authorId = value
        End Set
    End Property

<DataMember(Name:="tags")> _
    Public Property Tags() As String
        Get
            Return _tags
        End Get
        Set(ByVal value As String)
            _tags = value
        End Set
    End Property

End Class

<DataContract()> _
Public Class Media

Private _source As Uri

<DataMember(Name:="m")> _
    Public Property Source() As Uri
        Get
            Return _source
        End Get
        Set(ByVal value As Uri)
            _source = value
        End Set
    End Property

End Class

The following example shows how to take an existing stream and deserialize the JSON data into strongly-typed classes and output the source URL for each photo.

C# Example

// using System.Runtime.Serialization.Json;
        // using System.Text;
        private void ParsePhotoData(System.IO.Stream dataStream)
        {
            StringBuilder sb = new StringBuilder();
            DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(Photos));
            Photos photos = serializer.ReadObject(dataStream) as Photos;

if (photos != null && photos.Items != null)
            {
                sb.Append("Photo count=" + photos.Items.Count.ToString() + Environment.NewLine);

foreach(Photo photo in photos.Items)
                {
                    if (photo.Media != null)
                    {
                        sb.Append(photo.Media.Source + Environment.NewLine);
                    }
                }  // foreach

Debug.WriteLine(sb.ToString());
            }  // if (photos != null && photos.Items != null)
            else
            {
                Debug.WriteLine(sb.ToString());
            }  // if (photos != null && photos.Items != null)
        }

Visual Basic Example

Using the `JsonObject` Class

You can also work with JSON data in a weakly typed manner using the JsonObject, JsonArray, and JsonPrimitive classes. These classes can be used in conjunction with LINQ to iterate over the data. Importing the System.Json.dll will increase your XAP approximately 21kB.

Example

The following example shows how to take an existing stream, and using the weakly typed JSON classes, sort the results and output some details.

Silverlight: Using Returned JSON

Overview

Using the DataContractJsonSerializer Class

Example

C# Example

Visual Basic Example

C# Example

Visual Basic Example

Using the JsonObject Class

Example

C# Example

Visual Basic Example

Further Reading

Using the `DataContractJsonSerializer` Class

Using the `JsonObject` Class