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ScriptManager.RegisterDataItem Method (Control, String, Boolean)

Sends custom data to a control during partial-page rendering, and indicates whether the data is in JavaScript Object Notation (JSON) format.

Namespace:  System.Web.UI
Assembly:  System.Web.Extensions (in System.Web.Extensions.dll)

public void RegisterDataItem(
	Control control,
	string dataItem,
	bool isJsonSerialized


Type: System.Web.UI.Control

The page control that is receiving the data.

Type: System.String

The data that is sent to the control.

Type: System.Boolean

true to indicate that dataItem is serialized as JSON; otherwise, false.


control is null.


The RegisterDataItem method is called during a postback.


dataItem is already registered for control.

You use the RegisterDataItem method to send data from the server to the client during asynchronous postbacks, regardless of whether the control receiving the data is inside an UpdatePanel control.

If the dataItem parameter that you register for control is not serialized as JSON, set the isJsonSerialized parameter to false. This avoids the need to use the eval function for each string that is sent to the client. For more information about the JSON format, see the Introducing JSON Web site.

The RegisterDataItem method can be called only during an asynchronous postback. To determine whether a postback is asynchronous, use the IsInAsyncPostBack property.

The data items that are registered by using the RegisterDataItem method can be accessed in client script during the pageLoading, pageLoaded, and endRequest events of the PageRequestManager object. When you handle these events, the custom data is passed in an event argument object. For example, if you provide a handler for the pageLoading event, the custom data is passed in the PageLoadingEventArgs class, which exposes a dataItems property.

The following example shows how to send data to two Label controls on a page during an asynchronous postback. The Label controls are not inside an UpdatePanel control. This example shows the overload that does not take the isJsonSerialized parameter. Otherwise, the procedure for retrieving the dataItems property of the PageLoadingEventArgs object is the same as if you did not use that overload.


The data that is sent in this example is for illustration only. In a real-world application, you would use the RegisterDataItem method to send custom data from the server. For example, you could use the data item to send information about whether to hide or show client elements that are not inside an UpdatePanel control.

<%@ Page Language="C#" %>

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

<script runat="server">

    protected void Page_Load(object sender, EventArgs e)
        if (ScriptManager1.IsInAsyncPostBack)
            System.Web.Script.Serialization.JavaScriptSerializer json =
                new System.Web.Script.Serialization.JavaScriptSerializer();
            ScriptManager1.RegisterDataItem(Label1, DateTime.Now.ToString());
            ScriptManager1.RegisterDataItem(Label2, json.Serialize("more data"), true);

<html xmlns="" >
<head runat="server">
    <title>ScriptManager RegisterDataItem Example</title>
    <form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server" />
    <script type="text/javascript" language="javascript">
        function PageLoadingHandler(sender, args) {
            var dataItems = args.get_dataItems();
            if ($get('Label1') !== null)
                $get('Label1').innerHTML = dataItems['Label1'];
            if ($get('Label2') !== null)
                $get('Label2').innerHTML = dataItems['Label2'];
    <asp:UpdatePanel ID="UpdatePanel1" UpdateMode="Conditional" runat="server">
       UpdatePanel content.
       <asp:Button ID="Button1" Text="Submit" runat="server" />
    <hr />
    <asp:Label ID="Label1" runat="server" /> <br />
    <asp:Label ID="Label2" runat="server" />

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