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ClientScriptManager.IsStartupScriptRegistered Method (Type, String)

Determines whether the startup script is registered with the Page object using the specified key and type.

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

public bool IsStartupScriptRegistered(
	Type type,
	string key
)

Parameters

type
Type: System.Type

The type of the startup script to search for.

key
Type: System.String

The key of the startup script to search for.

Return Value

Type: System.Boolean
true if the startup script is registered; otherwise, false.

ExceptionCondition
ArgumentNullException

The startup script type is null.

Call this method before calling the RegisterStartupScript method to avoid registering duplicate scripts. This is particularly important if the script requires a large amount of server resources to create.

A client startup script is uniquely identified by its key and its type. Scripts with the same key and type are considered duplicates.

The following code example demonstrates the use of the IsStartupScriptRegistered method. Note that, if the logic to check for the existing startup script block were removed, there would not be two duplicate startup scripts in the HTML source code of the rendered page because the RegisterStartupScript method checks for duplicates. The benefit of checking is to reduce unnecessary computation.

<%@ Page Language="C#"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<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.'} </");
      cstext2.Append("script>");
      cs.RegisterClientScriptBlock(cstype, csname2, cstext2.ToString(), false);
    }
  }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
  <head>
    <title>ClientScriptManager Example</title>
  </head>
  <body>
     <form id="Form1"
         runat="server">
        <input type="text" id="Message" /> <input type="button" value="ClickMe" onclick="DoClick()" />
     </form>
  </body>
</html>

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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