Register Client script in ASP.NET

Introduction

Registering Client script from server itself useful when , you want certain java script to be executed when page finished loading or when user does a submit on the form .

Background

To get the complete idea about the clientside java script registration from server , u go through the URL http://msdn2.microsoft.com/en-us/library/ms178207.aspx

Using the code

You have a clientscriptmanager object on each aspx page you have . the object name is ClientScript , using ClientScript you can register the script in 4 modes

1. RegisterClientScriptBlock:-Adds Script to the top of the page

2.RegisterClientScriptInclude:- Refer to a external .js file

3.RegisterStartupScript:- script is registered before onload event of a page

4. RegisterOnSubmitStatement:- Script is registered on onSubmit event of page

Have a look at the following example below which uses startupscript in my project, I used this one because I needed script to be executed and load a activex object before page is loaded.

if (!ClientScript.IsClientScriptBlockRegistered("exampleScript"))
    ClientScript.RegisterStartupScript(this.GetType(), "exampleScript","
<script language = "'javascript'">
alert('you just registered the start up script')
</script>
");

 //you can also do the  Add script on the events of the controls , like button click
 //I wrote a generic method for adding confirm box to the web controls  as shown below

public static void ConfirmMessageBox(ref System.Web.UI.WebControls.WebControl webControl, string message, string webControlName, string eventName)
{

StringBuilder sb = new StringBuilder();
sb.AppendFormat("var str = trim(document.forms[0].{0}.value);", webControlName);
sb.Append("if(str != null)");
sb.Append("{");
sb.Append("if(str != '')");
sb.Append("{");
sb.AppendFormat("var bRet = confirm('{0}');", message);
sb.Append("if(!bRet)");
sb.AppendFormat("document.forms[0].{0}.value = '';", webControlName);
sb.Append("return bRet;");
sb.Append("}");
sb.Append("}");

webControl.Attributes.Add(eventName, sb.ToString());

}
//you can add this script to any textbox or button control  on page load as shown below
 
WebControl control = (WebControl)textBoxControl;
ConfirmMessageBox(ref control, "Are you sure , you want to create this domain",
textBoxControl.ClientID, "onblur");

//Hope this helps in getting better understanding of the client side script registration from server