JavaScriptConverter Class


Provides an abstract base class for a custom type converter.

public ref class JavaScriptConverter abstract
public abstract class JavaScriptConverter
type JavaScriptConverter = class
Public MustInherit Class JavaScriptConverter


The following example shows how to create a custom converter for the ListItemCollection class.

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Web.UI.WebControls;
using System.Collections;

namespace System.Web.Script.Serialization.CS
    public class ListItemCollectionConverter : JavaScriptConverter

        public override IEnumerable<Type> SupportedTypes
            //Define the ListItemCollection as a supported type.
            get { return new ReadOnlyCollection<Type>(new List<Type>(new Type[] { typeof(ListItemCollection) })); }

        public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer)
            ListItemCollection listType = obj as ListItemCollection;

            if (listType != null)
                // Create the representation.
                Dictionary<string, object> result = new Dictionary<string, object>();
                ArrayList itemsList = new ArrayList();
                foreach (ListItem item in listType)
                    //Add each entry to the dictionary.
                    Dictionary<string, object> listDict = new Dictionary<string, object>();
                    listDict.Add("Value", item.Value);
                    listDict.Add("Text", item.Text);
                result["List"] = itemsList;

                return result;
            return new Dictionary<string, object>();

        public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)
            if (dictionary == null)
                throw new ArgumentNullException("dictionary");

            if (type == typeof(ListItemCollection))
                // Create the instance to deserialize into.
                ListItemCollection list = new ListItemCollection();

                // Deserialize the ListItemCollection's items.
                ArrayList itemsList = (ArrayList)dictionary["List"];
                for (int i=0; i<itemsList.Count; i++)

                return list;
            return null;
Imports System.Collections.Generic
Imports System.Collections.ObjectModel
Imports System.Web.UI.WebControls
Imports System.Collections

Namespace System.Web.Script.Serialization.VB

    Public Class ListItemCollectionConverter
        Inherits JavaScriptConverter

        Public Overrides ReadOnly Property SupportedTypes() As _
            System.Collections.Generic.IEnumerable(Of System.Type)
                ' Define the ListItemCollection as a supported type.
                Return New ReadOnlyCollection(Of Type)(New List(Of Type) _
                (New Type() {GetType(ListItemCollection)}))
            End Get
        End Property

        Public Overrides Function Serialize(ByVal obj As Object, _
            ByVal serializer As JavaScriptSerializer) As _
            System.Collections.Generic.IDictionary(Of String, Object)

            Dim listType As ListItemCollection = CType(obj, ListItemCollection)

            If Not (listType Is Nothing) Then

                ' Create the representation.
                Dim result As New Dictionary(Of String, Object)

                Dim itemsList As New ArrayList()
                Dim item As ListItem
                For Each item In listType
                    ' Add each entry to the dictionary.
                    Dim listDict As New Dictionary(Of String, Object)
                    listDict.Add("Value", item.Value)
                    listDict.Add("Text", item.Text)
                Next item
                result("List") = itemsList

                Return result
            End If
            Return New Dictionary(Of String, Object)
        End Function

        Public Overrides Function Deserialize(ByVal dictionary As _
            System.Collections.Generic.IDictionary(Of String, Object), _
            ByVal type As System.Type, ByVal serializer As JavaScriptSerializer) As Object

            If dictionary Is Nothing Then
                Throw New ArgumentNullException("dictionary")
            End If

            If type Is GetType(ListItemCollection) Then
                ' Create the instance to deserialize into.
                Dim list As New ListItemCollection()

                ' Deserialize the ListItemCollection's items.
                Dim itemsList As ArrayList = CType(dictionary("List"), ArrayList)
                Dim i As Integer
                For i = 0 To itemsList.Count - 1
                    list.Add(serializer.ConvertToType(Of ListItem)(itemsList(i)))
                Next i

                Return list
            End If

            Return Nothing

        End Function
    End Class
End Namespace


The JavaScriptConverter class enables you to implement serialization and deserialization processes for managed types that are not natively supported by the JavaScriptSerializer class. You can also use JavaScriptConverter when you need more control over the serialization and deserialization process.

The SupportedTypes property indicates the types for which a custom converter provides converter services.

To indicate that a custom converter must be used by the JavaScriptSerializer instance, you must register the converter with the instance. If you are using the JavaScriptSerializer class directly, you should use the RegisterConverters method to register the converter. Otherwise, if you are invoking Web methods from ECMAScript (JavaScript) and you want to use the custom converter, you can register it by adding a converters element in the configuration file. For more information, see How to: Configure ASP.NET Services in Microsoft Ajax.

When the JavaScriptSerializer instance is serializing a type for which it has a custom converter registered, the serializer calls the Serialize method. Similarly, when the JavaScriptSerializer instance is deserializing a JavaScript Object Notation (JSON) string and recognizes that a type inside the JSON string has a custom converter associated with it, the serializer calls the Deserialize method.

Notes to Implementers

When you inherit from JavaScriptConverter, you must override the following members:



Initializes a new instance of the JavaScriptConverter class.



When overridden in a derived class, gets a collection of the supported types.


Deserialize(IDictionary<String,Object>, Type, JavaScriptSerializer)

When overridden in a derived class, converts the provided dictionary into an object of the specified type.


Determines whether the specified object is equal to the current object.

(Inherited from Object)

Serves as the default hash function.

(Inherited from Object)

Gets the Type of the current instance.

(Inherited from Object)

Creates a shallow copy of the current Object.

(Inherited from Object)
Serialize(Object, JavaScriptSerializer)

When overridden in a derived class, builds a dictionary of name/value pairs.


Returns a string that represents the current object.

(Inherited from Object)

Applies to

See also