In order to call the JavaScript function from Code Behind without using ScriptManager, one has to make use of the RegisterStartupScript method of the ClientScript class in ASP.Net using C# and VB.Net. The following HTML Markup consists of an ASP.Net Button and a Label control.

The main difference is that the RegisterStartupScript method places the JavaScript at the bottom of the ASP.NET page right before the closing element. The RegisterClientScriptBlock method places the JavaScript directly after the opening element in the page.

RegisterClientScriptBlock(Control, Type, String, String, Boolean) Registers a client script block with the ScriptManager control for use with a control that is inside an UpdatePanel control, and then adds the script block to the page.

RegisterStartupScript(Control, Type, String, String, Boolean) Registers a startup script block for a control that is inside an UpdatePanel by using the ScriptManager control, and adds the script block to the page.

A startup script is a file that performs tasks during the startup process of a virtual machine (VM) instance. Startup scripts can apply to all VMs in a project or to a single VM. For Linux startup scripts, you can use bash or non-bash file.

ScriptManager is a server-side control that sits on your Web Form and enables the core of ASP.NET AJAX. Its primary role is the arbitration of all other ASP.NET AJAX controls on the Web Form and the addition of the right scripting libraries to the Web browser so that the client portion of ASP.NET AJAX can function.

1. protected void UpdateTime(object sender, EventArgs e)
2. string time = DateTime.Now.ToString(“hh:mm:ss tt”);
3. string script = “window.onload = function() { UpdateTime(‘” + time + “‘); };”;
4. ClientScript.RegisterStartupScript(this.GetType(), “UpdateTime”, script, true);

script to the menu entry “Settings/-Edit startup script”. And don’t forget that Code::Blocks conveniently allows you to edit the edit_startup_script. script at any time. All you have to do is keep SHIFT pressed while clicking on the “Edit startup script” menu item ;).

If you want to register a startup script that does not pertain to partial-page updates, and if you want to register the script only one time during initial page rendering, use the RegisterStartupScript method of the ClientScriptManager class. You can get a reference to the ClientScriptManager object from the ClientScript property of the page.

RegisterStartupScript (Type, String, String, Boolean) Registers the startup script with the Page object using a type, a key, a script literal, and a Boolean value indicating whether to add script tags.

To register a startup script block every time that an asynchronous postback occurs, use the RegisterStartupScript (Page, Type, String, String, Boolean) overload of this method.

Attempting to register a script that is already registered does not create a duplicate of the script. Call the IsStartupScriptRegistered method to determine whether a startup script with a given key and type pair is already registered and avoid unnecessarily attempting to add the script.