IsClientScriptBlockRegistered Method
Collapse the table of content
Expand the table of content

Page.IsClientScriptBlockRegistered Method (String)

Note: This API is now obsolete.

Determines whether the client script block with the specified key is registered with the page.

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

[ObsoleteAttribute("The recommended alternative is ClientScript.IsClientScriptBlockRegistered(string key).")]
public bool IsClientScriptBlockRegistered(
	string key


Type: System.String

The string key of the client script to search for.

Return Value

Type: System.Boolean

true if the script block is registered; otherwise, false.

Call this method before calling Page.RegisterClientScriptBlock to avoid unnecessarily assembling the client-side script. This is particularly important if the script requires a large amount of server resources to create.

The IsClientScriptBlockRegistered method has been deprecated. Use the IsClientScriptBlockRegistered method in the ClientScriptManager class.

The following code example demonstrates the use of the RegisterClientScriptBlock method in conjunction with the IsClientScriptBlockRegistered method. If the ECMAScript written in the code declaration block has not already been registered, as determined by IsClientScriptBlockRegistered, then a RegisterClientScriptBlock call is made.

<%@ Page Language="C#"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
<script runat="server">
  public void Page_Load(Object sender, EventArgs e)
    String csname1 = "PopupScript";
    String csname2 = "ButtonClickScript";

    if (!IsClientScriptBlockRegistered(csname1))
        String cstext1 = "<script type=\"text/javascript\">" +
            "alert('Hello World');</" + "script>";
        RegisterStartupScript(csname1, cstext1);

    if (!IsClientScriptBlockRegistered(csname2))
      StringBuilder cstext2 = new StringBuilder();
      cstext2.Append("<script type=\"text/javascript\"> function DoClick() {");
      cstext2.Append("Form1.Message.value='Text from client script.'} </");
      RegisterClientScriptBlock(csname2, cstext2.ToString());
<html  >
    <title>RegisterClientScriptBlock Example</title>
     <form id="Form1"
        <input type="text" id="Message" /> <input type="button" value="ClickMe" onclick="DoClick()" />

.NET Framework
Available since 1.1
Return to top
© 2015 Microsoft