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ClientScriptManager Class

Defines methods for managing client scripts in Web applications.

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

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[AspNetHostingPermissionAttribute(SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)]
public sealed class ClientScriptManager

The ClientScriptManager class is used to manage client scripts and add them to Web applications. You can get a reference to the ClientScriptManager class from the ClientScript property of the Page object.

You can add a client script to a Web page declaratively by including the script in the HTML markup of the page. However, there are situations when adding client script dynamically is needed. To add a script dynamically, use the RegisterClientScriptBlock method, the RegisterClientScriptInclude method, the RegisterStartupScript method, or the RegisterOnSubmitStatement method, depending on when and how you want to add the script. For more information, see How to: Add Client Script Dynamically to ASP.NET Web Pages.

The ClientScriptManager class uniquely identifies scripts by a key String and a Type. Scripts with the same key and type are considered duplicates. Using the script type helps to avoid confusing similar scripts from different user controls that might be in use on the page.

The ClientScriptManager class can be used to invoke client callbacks in situations when it is desirable to run server code from the client without performing a postback. This is referred to as performing an out-of-band callback to the server. In a client callback, a client script function sends an asynchronous request to an ASP.NET Web page. The Web page runs a modified version of its normal life cycle to process the callback. Use the GetCallbackEventReference method to obtain a reference to a client function that, when invoked, initiates a client callback to a server event. For more information, see Implementing Client Callbacks Programmatically Without Postbacks in ASP.NET Web Pages.


Script callbacks will not work in older browsers that do not support the Document Object Model (DOM), and they require that ECMAScript is enabled on the client. To check if the browser supports callbacks, use the SupportsCallback property, which is accessible through the Browser property of the ASP.NET intrinsic Request object.

Use the GetPostBackEventReference method and the GetPostBackClientHyperlink method to define a client postback event. These methods enable client script functions, when invoked, to cause the server to post back to the page. A client postback event is different from a client callback in that the Web page completes a normal life cycle to process the client postback event.


If you are using a Button control and the UseSubmitBehavior property is set to false, then you can use the GetPostBackEventReference method to return the client postback event for the Button control.

The OnClientClick property of the Button control, ImageButton control, and LinkButton control can be used to run client script.

The following code example demonstrates the use of the RegisterClientScriptBlock method of the ClientScriptManager class. Two client scripts are defined in the page: PopupScript, which displays an alert message when the page is loaded, and ButtonClickScript, which defines a client handler for an HTML button's onClick event.

<%@ Page Language="C#"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
<script runat="server">
  public void Page_Load(Object sender, EventArgs e)
    // Define the name and type of the client scripts on the page.
    String csname1 = "PopupScript";
    String csname2 = "ButtonClickScript";
    Type cstype = this.GetType();

    // Get a ClientScriptManager reference from the Page class.
    ClientScriptManager cs = Page.ClientScript;

    // Check to see if the startup script is already registered. 
    if (!cs.IsStartupScriptRegistered(cstype, csname1))
      String cstext1 = "alert('Hello World');";
      cs.RegisterStartupScript(cstype, csname1, cstext1, true);

    // Check to see if the client script is already registered. 
    if (!cs.IsClientScriptBlockRegistered(cstype, csname2))
      StringBuilder cstext2 = new StringBuilder();
      cstext2.Append("<script type=\"text/javascript\"> function DoClick() {");
      cstext2.Append("Form1.Message.value='Text from client script.'} </");
      cs.RegisterClientScriptBlock(cstype, csname2, cstext2.ToString(), false);
<html xmlns="" >
    <title>ClientScriptManager Example</title>
     <form id="Form1"
        <input type="text" id="Message" /> <input type="button" value="ClickMe" onclick="DoClick()" />


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 XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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, 3.0, 2.0