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Implement Script Callback Framework in ASP.NET 1.x

, 2 Aug 2004
It allows calls to server events from client script code without causing the page to post back and refresh.
using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Text;
using System.Collections;
using System.Collections.Specialized;
using System.ComponentModel;


namespace ScriptCallbackFramework
{
	/// <summary>
	/// Implemenet IClientCallbackEventHandler in the Server Control
	/// </summary>
	[DefaultProperty("Text"),
	ToolboxData("<{0}:AgeCalculator runat=server></{0}:AgeCalculator>")]
	public class AgeCalculator : Control, IClientCallbackEventHandler, IPostBackEventHandler, IPostBackDataHandler
	{	
		#region OnInit

		protected override void OnInit(EventArgs e)
		{
			base.OnInit(e);
			if (Page != null)
			{
				Page.RegisterRequiresPostBack(this);
				
				string script = String.Empty;

				//	ShowAgeHandler JavaScript function
				script = "<script language=\"javascript\">function ShowAgeHandler(responseText, context) { alert(\"Your age is \" + responseText);  } </script>";
				Page.RegisterClientScriptBlock("ShowAgeHandler", script);
				
				//	ShowAgeErrorHandler JavaScript function
				script = "<script language=\"javascript\">function ShowAgeErrorHandler(responseText, context) { alert(\"Which year you were born?\"); if (context != null) context.value = \"\";  }</script>";
				Page.RegisterClientScriptBlock("ShowAgeErrorHandler", script);
			}		
		}
		
		#endregion
		
		#region OnLoad
		protected override void OnLoad(EventArgs e)
		{	
			Label l = new Label();
			l.Text = "Please enter your year of birth : ";
			Controls.Add(l);
			
			TextBox txtBox = new TextBox();
			txtBox.ID = "txtAge";
			txtBox.Width = 50;
			Controls.Add(txtBox);
			
			HtmlInputButton btn = new HtmlInputButton();
			btn.ID = "CalculateAgeButton";
			btn.Value = "Calculate Age";
			btn.Attributes["onclick"] = PageTemplate.GetAsyncCallbackEventReference
				(
					this,
					String.Format("document.getElementById('{0}').value", txtBox.UniqueID),
					"ShowAgeHandler",
					String.Format("document.getElementById('{0}')", txtBox.UniqueID),
					"ShowAgeErrorHandler"
				);
			Controls.Add(btn);
			
			base.OnLoad (e);
		}
		#endregion
		
		#region IClientCallbackEventHandler Members

		public string RaiseClientCallbackEvent(string eventArgument)
		{
			return Convert.ToString(DateTime.Now.Year - Convert.ToInt32(eventArgument));
		}
		
		#endregion

		#region IPostBackEventHandler Members

		public void RaisePostBackEvent(string eventArgument)
		{
			// TODO:  Add AgeCalculator.RaisePostBackEvent implementation
		}

		#endregion

		#region IPostBackDataHandler Members

		public void RaisePostDataChangedEvent()
		{
			// TODO:  Add AgeCalculator.RaisePostDataChangedEvent implementation
		}

		public bool LoadPostData(string postDataKey, NameValueCollection postCollection)
		{
			// TODO:  Add AgeCalculator.LoadPostData implementation
			return false;
		}

		#endregion
	}
}

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About the Author

Elvin Cheng

Singapore Singapore
Elvin Cheng is currently living in Woodlands, Singapore. He has been developing applications with the .NET Framework, using C# and ASP.NET since October 2002. Elvin specializes in building Real-time monitoring and tracking information system for Semi-conductor manufacturing industry. During his spare time, he enjoys reading books, watching movie and gym.
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Web03 | 2.8.141022.2 | Last Updated 3 Aug 2004
Article Copyright 2004 by Elvin Cheng
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