JavaScriptSerializer Class


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Json.NET should be used serialization and deserialization. Provides serialization and deserialization functionality for AJAX-enabled applications.

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


Public Class JavaScriptSerializer


Initializes a new instance of the JavaScriptSerializer class that has no type resolver.


Initializes a new instance of the JavaScriptSerializer class that has a custom type resolver.


Gets or sets the maximum length of JSON strings that are accepted by the JavaScriptSerializer class.


Gets or sets the limit for constraining the number of object levels to process.

System_CAPS_pubmethodConvertToType(Object, Type)

Converts the specified object to the specified type.

System_CAPS_pubmethodConvertToType(Of T)(Object)

Converts the given object to the specified type.

System_CAPS_pubmethodDeserialize(String, Type)

Converts a JSON-formatted string to an object of the specified type.

System_CAPS_pubmethodDeserialize(Of T)(String)

Converts the specified JSON string to an object of type T.


Converts the specified JSON string to an object graph.


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(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.)

System_CAPS_pubmethodRegisterConverters(IEnumerable(Of JavaScriptConverter))

Registers a custom converter with the JavaScriptSerializer instance.


Converts an object to a JSON string.

System_CAPS_pubmethodSerialize(Object, StringBuilder)

Serializes an object and writes the resulting JSON string to the specified StringBuilder object.


Returns a string that represents the current object.(Inherited from Object.)

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.

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

null (null 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 first example provides a simple illustration of how to serialize and deserialize data objects. It requires a class names Person which is shown below.

Imports System.Web.Script.Serialization

Public Class _Default
    Inherits Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
        Dim RegisteredUsers As New List(Of Person)()
        RegisteredUsers.Add(New Person With {.PersonID = 1, .Name = "Bryon Hetrick", .Registered = True})
        RegisteredUsers.Add(New Person With {.PersonID = 2, .Name = "Nicole Wilcox", .Registered = True})
        RegisteredUsers.Add(New Person With {.PersonID = 3, .Name = "Adrian Martinson", .Registered = False})
        RegisteredUsers.Add(New Person With {.PersonID = 4, .Name = "Nora Osborn", .Registered = False})

        Dim serializer As New JavaScriptSerializer()
        Dim serializedResult = serializer.Serialize(RegisteredUsers)
        ' Produces string value of:
        ' [
        '     {"PersonID":1,"Name":"Bryon Hetrick","Registered":true},
        '     {"PersonID":2,"Name":"Nicole Wilcox","Registered":true},
        '     {"PersonID":3,"Name":"Adrian Martinson","Registered":false},
        '     {"PersonID":4,"Name":"Nora Osborn","Registered":false}
        ' ]

        Dim deserializedResult = serializer.Deserialize(Of List(Of Person))(serializedResult)
        ' Produces List with 4 Person objects
    End Sub
End Class
Public Class Person
    Public Property PersonID As Integer
    Public Property Name As String
    Public Property Registered As Boolean
End Class

The next example shows a more complicated and complete project that uses 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...

.NET Framework
Available since 3.5

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

System.Web.Script.Serialization Namespace
Using Web Services in ASP.NET AJAX
Calling Web Services from Client Script in ASP.NET AJAX

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