RegisterClientScriptBlock Method
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Page.RegisterClientScriptBlock Method (String, String)

Note: This API is now obsolete.

Emits client-side script blocks to the response.

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

[ObsoleteAttribute("The recommended alternative is ClientScript.RegisterClientScriptBlock(Type type, string key, string script).")]
public virtual void RegisterClientScriptBlock(
	string key,
	string script


Type: System.String

Unique key that identifies a script block.

Type: System.String

Content of script that is sent to the client.

The client-side script is emitted just after the opening tag of the Page object's <form runat= server> element. Be sure to include opening and closing <script> elements around the script block string specified in the script parameter.

Because this method uses a key to identify the script block, the script block does not have to be emitted to the output stream each time it is requested by a different server control instance. Using a key also decreases the likelihood of different controls' script blocks interfering with each other.

Any script blocks with the same key parameter values are considered duplicates.


Remember to include HTML comment tags around your script so that it will not be rendered if the requesting browser does not support scripts.

The RegisterClientScriptBlock method has been deprecated. Use the RegisterClientScriptBlock method in the ClientScriptManager class instead.

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