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JavaScriptSerializer Class

Provides serialization and deserialization functionality for AJAX-enabled applications.

Namespace:  System.Web.Script.Serialization
Assembly:  System.Web.Extensions (in System.Web.Extensions.dll)

<AspNetHostingPermissionAttribute(SecurityAction.InheritanceDemand, Level := AspNetHostingPermissionLevel.Minimal)> _
<AspNetHostingPermissionAttribute(SecurityAction.LinkDemand, Level := AspNetHostingPermissionLevel.Minimal)> _
Public Class JavaScriptSerializer
Dim instance As JavaScriptSerializer

The JavaScriptSerializer class is used internally by the asynchronous communication layer to serialize and deserialize the data that is passed between the browser and the Web server. You cannot access that instance of the serializer. However, this class exposes a public API. Therefore, you can use the class when you want to work with JavaScript Object Notation (JSON) in managed code.

To serialize an object, use the Serialize method. To deserialize a JSON string, use the Deserialize(Of T) or DeserializeObject methods. To serialize and deserialize types that are not natively supported by JavaScriptSerializer, implement custom converters by using the JavaScriptConverter class. Then register the converters by using the RegisterConverters method.

Mapping Between Managed Types and JSON

The following table shows the mapping between managed types and JSON for the serialization process. These managed types are natively supported by JavaScriptSerializer. When you are deserializing from a JSON string to a managed type, the same mapping applies. However, deserialization can be asymmetric; not all serializable managed types can be deserialized from JSON.


A multidimensional array is serialized as a one-dimensional array, and you should use it as a flat array.

Managed type

JSON equivalent

String (UTF-8 encoding only).




Single null char (such as, \0 )



Boolean. Represented in JSON as true or false

Nothing (Nothing object references and Nullable value types).

A string value of null


A string value of null

Primitive numeric (or numeric-compatible) types: Byte, SByte, Int16, Int32, Int64, UInt16, UInt32, UInt64, Double, and Single. The culture-invariant string representation is used.



Date object, represented in JSON as "\/Date(number of ticks)\/". The number of ticks is a positive or negative long value that indicates the number of ticks (milliseconds) that have elapsed since midnight 01 January, 1970 UTC.

The maximum supported date value is MaxValue (12/31/9999 11:59:59 PM) and the minimum supported date value is MinValue (1/1/0001 12:00:00 AM).

Enumerations of integer type

Integer equivalent of the enumeration value

Types that implement IEnumerable or System.Collections.Generic.IEnumerable(Of T) that are not also implementations of IDictionary or System.Collections.Generic.IDictionary(Of TKey, TValue). This includes types such as Array, ArrayList, and List(Of T).

Array that uses JSON array syntax

Types that implement IDictionary or System.Collections.Generic.IDictionary(Of TKey, TValue). This includes types such as Dictionary(Of TKey, TValue) and Hashtable.

JavaScript object that uses JSON dictionary syntax

Custom concrete (non-abstract) types that have public instance properties that have get accessors or public instance fields.

Note that public write-only properties, public property or public field attributes marked with ScriptIgnoreAttribute, and public indexed properties in these types are ignored.

JavaScript object that uses JSON dictionary syntax. A special metadata property named "__type" is included to ensure correct deserialization. Make sure that public instance properties have get and set accessors to ensure correct deserialization.


String representation of a GUID


String representation of the return value of GetComponents

The following example shows how to use the JavaScriptSerializer class to save and restore the state of an object by using JSON serialization. This code uses a custom converter that is provided for the JavaScriptConverter class.

<%@ Page Language="VB" %>
<%@ Import Namespace="System.Web.Script.Serialization" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">

<script runat="server">

    Dim serializer As JavaScriptSerializer

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
        serializer = New JavaScriptSerializer()

        ' Register the custom converter.
        serializer.RegisterConverters(New JavaScriptConverter() _
            {New System.Web.Script.Serialization.VB.ListItemCollectionConverter()})
    End Sub 

    Protected Sub saveButton_Click(ByVal sender As Object, ByVal e As EventArgs)
        ' Save the current state of the ListBox control.
        SavedState.Text = serializer.Serialize(ListBox1.Items)
        recoverButton.Enabled = True
        Message.Text = "State saved" 
    End Sub 

    Protected Sub recoverButton_Click(ByVal sender As Object, ByVal e As EventArgs)
        ' Recover the saved items of the ListBox control.         
        Dim recoveredList As ListItemCollection = _
            serializer.Deserialize(Of ListItemCollection)(SavedState.Text)
        Dim newListItemArray(recoveredList.Count - 1) As ListItem
        recoveredList.CopyTo(newListItemArray, 0)
        Message.Text = "Last saved state recovered." 
    End Sub 

    Protected Sub clearButton_Click(ByVal sender As Object, ByVal e As EventArgs)
        ' Remove all items from the ListBox control.
        Message.Text = "All items removed" 
    End Sub 

    Protected Sub ContactsGrid_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
        ' Get the currently selected row using the SelectedRow property. 
        Dim row As GridViewRow = ContactsGrid.SelectedRow

        ' Get the ID of the item selected. 
        Dim itemId As String = ContactsGrid.DataKeys(row.RowIndex).Value.ToString()
        Dim newItem As ListItem = New ListItem(row.Cells(4).Text, itemId)

        ' Check if the item already exists in the ListBox control. 
        If Not ListBox1.Items.Contains(newItem) Then 
            ' Add the item to the ListBox control.
            Message.Text = "Item added" 
            Message.Text = "Item already exists" 
        End If 

    End Sub 

    Private Function SearchItem(ByVal itemId As String) As Boolean 
        Dim i As Integer 
        For i = 0 To ListBox1.Items.Count - 1
            If ListBox1.Items(i).Value = itemId Then 
                Return True 
            End If 
        Next i
        Return False 

    End Function 

    Protected Sub ContactsGrid_PageIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
        ContactsGrid.SelectedIndex = -1
    End Sub 

    Protected Sub searchButton_Click(ByVal sender As Object, ByVal e As EventArgs)
        ContactsGrid.SelectedIndex = -1
        ContactsGrid.PageIndex = 0
    End Sub 

    Protected Sub CheckBox1_CheckedChanged(ByVal sender As Object, ByVal e As EventArgs)
        SavedState.Visible = CheckBox1.Checked
        StateLabel.Visible = CheckBox1.Checked
    End Sub

<html xmlns="" >
<head runat="server">
    <title>Save/Recover state</title>
    <style type="text/css">
        body {  font: 11pt Trebuchet MS;
                font-color: #000000;
                padding-top: 72px;
                text-align: center }

        .text { font: 8pt Trebuchet MS }
    <form id="form1" runat="server" defaultbutton="searchButton" defaultfocus="TextBox1">
            <span style="text-decoration: underline">
                                    Contacts Selection</span><br />
        <asp:ScriptManager runat="server" ID="ScriptManager1" />
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
                Type contact's first name:
                <asp:TextBox ID="TextBox1" runat="server" />
                <asp:Button ID="searchButton" runat="server" Text="Search" OnClick="searchButton_Click" />&nbsp;
                <br />
                <br />
                <table border="0" width="100%">
                        <td style="width:50%" valign="top" align="center">
                            <b>Search results:</b><br />
                            <asp:GridView ID="ContactsGrid" runat="server" AutoGenerateColumns="False"
                                CellPadding="4" DataKeyNames="ContactID" DataSourceID="SqlDataSource1"
                                OnSelectedIndexChanged="ContactsGrid_SelectedIndexChanged" ForeColor="#333333" GridLines="None" AllowPaging="True" PageSize="7" OnPageIndexChanged="ContactsGrid_PageIndexChanged">
                                    <asp:CommandField ShowSelectButton="True" ButtonType="Button" />
                                    <asp:BoundField DataField="ContactID" HeaderText="ContactID" SortExpression="ContactID" Visible="False" />
                                    <asp:BoundField DataField="FirstName" HeaderText="FirstName" SortExpression="FirstName" />
                                    <asp:BoundField DataField="LastName" HeaderText="LastName" SortExpression="LastName" />
                                    <asp:BoundField DataField="EmailAddress" HeaderText="EmailAddress" SortExpression="EmailAddress" />
                                <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
                                <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
                                <AlternatingRowStyle BackColor="White" ForeColor="#284775" />
                                <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
                                <EditRowStyle BackColor="#999999" />
                                <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
                                <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
                                <EmptyDataTemplate>No data found.</EmptyDataTemplate>
                            <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:AdventureWorksConnectionString %>"
                                SelectCommand="SELECT ContactID, FirstName, LastName, EmailAddress FROM Person.Contact WHERE (UPPER(FirstName) = UPPER(@FIRSTNAME))" >
                                    <asp:ControlParameter Name="FIRSTNAME" ControlId="TextBox1" Type="String" />
                        <td valign="top">
                            <b>Contacts list:</b><br />
                        <asp:ListBox ID="ListBox1" runat="server" Height="200px" Width="214px" /><br />
                        <asp:Button ID="saveButton" runat="server" Text="Save state" OnClick="saveButton_Click" ToolTip="Save the current state of the list" />
                        <asp:Button ID="recoverButton" runat="server" Text="Recover saved state" OnClick="recoverButton_Click" Enabled="false" ToolTip="Recover the last saved state" />
                        <asp:Button ID="clearButton" runat="server" Text="Clear" OnClick="clearButton_Click" ToolTip="Remove all items from the list" /><br />
                            <br />
                            <asp:CheckBox ID="CheckBox1" runat="server" Checked="True" OnCheckedChanged="CheckBox1_CheckedChanged"
                                Text="Show saved state" AutoPostBack="True" /></td>
                        <td colspan="2">
                            <br />
                            <br />
                            <hr />
                            Message: <asp:Label ID="Message" runat="server" ForeColor="SteelBlue" />&nbsp;&nbsp;<br />
                            <asp:Label ID="StateLabel" runat="server" Text="State:"></asp:Label>
                            <asp:Label ID="SavedState" runat="server"/><br />                        
        <asp:UpdateProgress ID="UpdateProgress1" runat="server">
                <asp:Image ID="Image1" runat="server" ImageUrl="..\images\spinner.gif" />&nbsp;Processing...


Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5