Using Associative Arrays for Client-side Caching using AJAX & Javascript

Introduction

This article shows you a useful technique to cache some of that page data on the browser in-memory. Since we use Ajax, the page is not reloaded each time. This prevents the cache from being invalidated on each round-trip. Client-side caching is sometimes required for performance reasons and also to take the load off of the DBMS. Since most modern PCs have plenty of RAM to spare, client-side caching becomes an important weapon in the modern programmer's arsenal of tricks.

With the advent of Ajax, application data can be maintained on the client without the use of ViewStates (aka hidden fields) or to a lesser degree, cookies. As any experienced developer will tell you, ViewState is a double-edged sword. Indiscriminate use of ViewStates can really have a detrimental effect on performance - what with the Viewstate payload ferried to and from the server with every postback.

The accompanying code can be extended to use record data too, via Javascript and the presentation logic can also be hived off to a Javascript routine on the client. We could even pipe XML down to the client and it could be parsed and presented through client-side script.

To keep this sample code easy to comprehend, I have rendered the tabular data from within the Web Service itself - which may not be architecturally optimal. Since this is not a treatise on design best-practices, I have taken the liberty of cutting corners here and there for the sake of brevity.

img width="36" height="42" style="float: left;" alt="Screenshot - article1.gif" src="Client-sideCaching/article1.gif" />We use JavaScript associative arrays to maintain our client-side cache. One thing to be noted about JS associative arrays is that once you associate a string key with an array, there is no way to iterate through the array using indexes. Supposing you are using it like this:asarray["akey"] = <value> there is no way you can revert to accessing the elements by their ordinal position like this: var anyvar = asarray[0].

Calling Server Side Code from Client Side using Ajax

Introduction

Using Microsoft ASP.NET AJAX is to call ASP.NET Web services (*.asmx files) from the browser by using client script. The script can call a webservice containing server-based methods (Web methods) and invoke these methods without a postback and without refreshing the whole page. The option we are going to use in this article involves PageMethods. A PageMethod is basically a public static method that is exposed in the code-behind of an aspx page and is callable from the client script. PageMethods are annotated with the [WebMethod] attribute. The page methods are rendered as inline JavaScript

A cool'n'simple search page using Google AJAX Search API, and some DHTML

Introduction

In this article I'll demonstrate how easy it is, to create a usable webpage with some advanced technologies (such as fast asynchronous web search) in a very simple way, using a public API.

Salajax: simple Ajax library solving back button and bookmarks for Ajax web applications

Salajax is a simplified Ajax library that handles back buttons, bookmarks and is extremely simple to use. Yes, Ajax is great. It does have some minor issues though, like the back button not working and the inability to use bookmarks. This library provides a simple class that will handle all these issues and more, without you having to think about it too much.
The Simple Ajax Library Ajax class (Salajax) tries to:

• Make the back button work with Ajax
• Make bookmarks work with Ajax
• Run JavaScript contained in the Ajax response
• Keep the .NET Viewstate
• Submit forms as an Ajax request
• Specify OnStart and OnEnd JavaScript functions to call
• Specify an OnError JavaScript function to call when the Ajax response is an error
• Set the HTML to display when updating a div with an Ajax request
• Set the HTML to display when there is an error making the Ajax request
• Be extremely simple to use

Basically, I'm hoping that the Salajax class will make it very easy to do everything and anything you could possibly want to do using Ajax.

Dragging and dropping with ASP.NET 2.0 and Atlas

Introduction

This tutorial is intended to help readers understand how certain aspects of Microsoft's new AJAX Extensions technology works. AJAX Extensions is intended to simplify the development of AJAX-style functionality. As with all technologies, however, to use a tool well, it is important to understand the underlying technology that Atlas abstracts. One of the key ASP.NET AJAX abstractions is the new XML markup syntax developed to make coding with AJAX easier (originally included with the core Atlas files, XML markup is now a part of the CTP called AJAX Futures). With XML markup, developers can modify their code declaratively. However, there are times when a developer may want to be able to change her code programmatically, and in order to accomplish this, she will need to understand that underneath the markup abstraction, she is actually dealing with good 'ol JavaScript and some custom JavaScript libraries developed by Microsoft. In order to demonstrate the relationship between the Atlas declarative model and the programmatic model, I will go through a series of examples in which the same task will be accomplished both declaratively and programmatically. I will be demonstrating how to use the PreviewDragDrop library file to perform basic drag-drop operations as well as setting up drop zones.

Ajax AutoComplete in ASP.NET

Without using AjaxControlToolKit, we can implement AutoComplete Extender using pure Ajax Call. This article explains how to do make AutoComplete Extender.

OnKeyUp event helps you to fetch data from database with Ajax call. Here one Handler.ashx handles the AJAX request form Client. I add a Class file to handle database operations to better coding practice. Below I explain the database helper Class. Class has one method:

GetTable(string sqlQuery) 

Making Cross Domain jQuery AJAX Calls

Today's web browsers do not allow web pages to make cross-domain Ajax calls. By this, I mean that if you are at www.ajax.com and try to make an Ajax call (a call using the XmlHttpRequest object), the browser would not allow this to happen. Why? For security purposes that I cannot currently name.

However, at some point you get to a project where you're interfacing this third-party site that needs to talk to your main site, or some other similar situation where the only way you're going to get the data you need from point a to point b is with some JavaScript magic. Here is how to accomplish it.