Welcome!

Machine Learning Authors: William Schmarzo, Elizabeth White, Liz McMillan, Pat Romanski, James Carlini

Related Topics: Machine Learning , Microsoft Cloud

Machine Learning : Article

Google Maps! AJAX-Style Web Development Using ASP.NET

Taking asynchronous Web forms to the next level

As you can see from the above code sample, it is quite simple to use the XMLHttp object in a stand-alone manner. However, integrating the XMLHttp into the rest of the HttpPage life cycle is difficult - for example, how does one ensure that the server-side method being called has access to the state of other controls on the page? For the state of the controls to be correctly initialized, the callback handling on the server needs to go through a similar HttpPage life cycle as the postback. The other challenge in using the XMLHttp object directly is that as developers we need to account for different browser types. Fortunately, ASP.NET 2.0 provides a reusable pattern that makes the callback functionality easily accessible. Note that several controls that ship with ASP.NET 2.0, including GridView, TreeView, etc., leverage the callback capability.

Figure 1 depicts how the callbacks are implemented in ASP.NET 2.0. Let us start from the server side. A new interface, ICallBackEventHandler, has been defined. Any ASPX page (or a control that intends to support client callbacks) needs to implement the ICallBackEventHandler interface. ICallBackEventHandler defines one method called RaiseCallbackEvent. This method takes one parameter of type string as the argument and returns a string.

On the client side, to initiate the callback, a special Javascript function needs to be invoked. You can obtain a reference to this special Javascript function by calling ClientScriptManager.GetCallbackEventReference (see the second and third entries in the References section). The call to GetCallbackEventReference results in a reference to callback. When invoking the callback, you pass one parameter of type string. This is consistent with server-side RaiseCallbackEvent signature. That is all you need to set up callbacks from the client. The rest of the magic to hook up the client callback to the server-side RaiseCallbackEvent method of ICallBackEventHandler is done by the framework. The aforementioned special Javascript function for initiating callback uses two additional parameters to be included as part of the postback data - __CALLBACKPARAM and __CALLBACKID, which represent the string parameter to pass to the call and the ID of the control, respectively. On the server, ASP.NET detects the presence of the two additional parameters and routes the request to the appropriate control, resulting in the invocation of the RaiseCallbackEvent method on the target control. To solve the aforementioned problem related to initialization of controls on the page, ASP.NET runtime follows a trimmed-down version of HttpPage life cycle when servicing a callback. This includes going through the specific stages of page initialization, view state loading, page loading, and callback event handling. Once the callback event is handled by the control, the rest of the HttpPage life cycle stages are skipped.

To help better understand the ASP.NET 2.0 callbacks, included is a simple progress bar control that relies on callbacks to determine the status of a given task on the server. Listing 1 displays the code for the ProgressBar control. To support client callbacks, this control implements the ICallbackEventHandler interface. For the purpose of the demo, the RaiseCallbackEvent method implementation simply looks up a counter stored in the session, increments the counter by one, and returns the new value to the client. Finally, Listing 2 is the Javascript code that is responsible for initiating the callback. It uses this.Page.ClientScript.GetCallbackEventReference to obtain a safe reference to the function needed to initiate the callback.

Using client callbacks provided in ASP.NET 2.0, it is relatively straightforward to implement the progress bar control, since the data passing between the control and the client is a simple string. However, as soon as we start adding other datatypes to the mix, we will run into mismatches between Javascript and .NET-type systems. Unfortunately, the callback implementation in ASP.NET 2.0 does not help with this issue. Applications that want to use multiple datatypes, simple and complex, will need to implement a custom scheme on their own.

Fortunately, this limitation can be overcome by using an open source library called AJAX.NET (see the fourth entry in the References section), AJAX.NET implements a proxy-based approach for calling the server-side functions. AJAX.Net defines a custom attribute called AJAXMethod. When a server-side method is decorated with the AJAXMethod, a Javascript-based client proxy is automatically generated by the HttpHandler that is part of AJAX.NET library. Unlike ASP.NET 2.0, which supports a single parameter of type string for callbacks, AJAX.Net supports integers, strings, double, DateTime, DataSets, etc.

An alternative to AJAX.NET for dealing with differences between the Javascript and .NET-type system is suggested by Bertrand Le Roy (see the fifth entry in the References section). He has created a server-side control called EcmaScriptObject that recreates the Javascript type system in .NET. The idea is to reproduce a client-side object graph in .NET. This approach makes better sense as the conversion is happening on the server.

Even if we have a type-safe way to invoke callbacks, more challenges remain. Javascript is the glue that holds all the pieces of the AJAX application together. Thus, there is increased reliance on Javascript. Unfortunately, even though Javascript is a powerful and versatile language, it does not lend itself easily to well-known object- oriented principles. This means it is harder to achieve code reuse. Please refer to the sixth entry in the References section for syntactic sugar added around Javascript to make it appear as traditional OO language. Even then, it is hard to implement features available in managed languages such as events and delegates.

The other difficulty, as discussed earlier, is the lack of a reusable framework to make the Javascript development more productive. For example, wouldn't it be nice to have access to a Javascript-based UI framework that hides the differences between different execution environments? Another example would be a set of classes that make it easy to invoke Web services in a secure manner (as opposed to hand coding the SOAP packets and using XMLHttp to transport them).

More Stories By Vishwas Lele

Vishwas Lele is a principal architect at Applied Information Sciences (www.appliedis.com), a system and software engineering company specializing in .NET-based solutions. Vishwas also serves as the MSDN Regional Director for the Washington, DC area.

Comments (17) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
Shabdar 03/25/08 11:57:26 AM EDT

If you are looking for Google Maps control for ASP.Net visit following link,

http://www.shabdar.org

This is a free open source control.

Steve 06/02/06 11:11:07 AM EDT

The title of the article is misleading. I see no mention of Google Maps in the content of the article in regards to ASP.NET.

I applaud the editors for coming up with such innovatively misleading bait to entice them to read the entire article, and all the embedded ads. Bravo!

AJAX News Desk 06/01/06 11:59:33 AM EDT

In the past few months, the design pattern of combining Asynchronous JavaScript and XML (AJAX) to develop highly interactive Web applications has been growing in popularity. High-profile Web applications such as Google Maps and A9 are currently leveraging the combination of these technologies to produce rich client-side user experiences. The individual technologies that compose AJAX are not recent developments; they have been around for some time and have been continuously updated and improved. However, it is the recent confluence of these technologies that is leading to interesting possibilities.

SYS-CON India News Desk 05/31/06 12:50:59 PM EDT

In the past few months, the design pattern of combining Asynchronous JavaScript and XML (AJAX) to develop highly interactive Web applications has been growing in popularity. High-profile Web applications such as Google Maps and A9 are currently leveraging the combination of these technologies to produce rich client-side user experiences. The individual technologies that compose AJAX are not recent developments; they have been around for some time and have been continuously updated and improved. However, it is the recent confluence of these technologies that is leading to interesting possibilities.

SYS-CON Italy News Desk 05/31/06 12:20:35 PM EDT

In the past few months, the design pattern of combining Asynchronous JavaScript and XML (AJAX) to develop highly interactive Web applications has been growing in popularity. High-profile Web applications such as Google Maps and A9 are currently leveraging the combination of these technologies to produce rich client-side user experiences. The individual technologies that compose AJAX are not recent developments; they have been around for some time and have been continuously updated and improved. However, it is the recent confluence of these technologies that is leading to interesting possibilities.

AJAX News Desk 05/31/06 11:49:13 AM EDT

In the past few months, the design pattern of combining Asynchronous JavaScript and XML (AJAX) to develop highly interactive Web applications has been growing in popularity. High-profile Web applications such as Google Maps and A9 are currently leveraging the combination of these technologies to produce rich client-side user experiences. The individual technologies that compose AJAX are not recent developments; they have been around for some time and have been continuously updated and improved. However, it is the recent confluence of these technologies that is leading to interesting possibilities.

not amused 02/23/06 03:57:06 AM EST

unreadable text thanks to floating add that is impossible to close

Sanjay Gupta 02/21/06 04:41:58 PM EST

Great explaination of the article.
I appreciate it!

Sanjay

SYS-CON Italy News Desk 02/19/06 05:53:45 PM EST

In the past few months, the design pattern of combining Asynchronous JavaScript and XML (AJAX) to develop highly interactive Web applications has been growing in popularity. High-profile Web applications such as Google Maps and A9 are currently leveraging the combination of these technologies to produce rich client-side user experiences. The individual technologies that compose AJAX are not recent developments; they have been around for some time and have been continuously updated and improved. However, it is the recent confluence of these technologies that is leading to interesting possibilities.

news 12/23/05 04:31:18 PM EST

In the past few months, the design pattern of combining Asynchronous JavaScript and XML (AJAX) to develop highly interactive Web applications has been growing in popularity. High-profile Web applications such as Google Maps and A9 are currently leveraging the combination of these technologies to produce rich client-side user experiences. The individual technologies that compose AJAX are not recent developments; they have been around for some time and have been continuously updated and improved. However, it is the recent confluence of these technologies that is leading to interesting possibilities.

SYS-CON UK News Desk 12/23/05 02:32:15 PM EST

Google Maps! Ajax-Style Web Development Using ASP.NET
In the past few months, the design pattern of combining Asynchronous JavaScript and XML (AJAX) to develop highly interactive Web applications has been growing in popularity. High-profile Web applications such as Google Maps and A9 are currently leveraging the combination of these technologies to produce rich client-side user experiences. The individual technologies that compose AJAX are not recent developments; they have been around for some time and have been continuously updated and improved. However, it is the recent confluence of these technologies that is leading to interesting possibilities.

AJAX News Desk 12/23/05 11:41:04 AM EST

In the past few months, the design pattern of combining Asynchronous JavaScript and XML (AJAX) to develop highly interactive Web applications has been growing in popularity. High-profile Web applications such as Google Maps and A9 are currently leveraging the combination of these technologies to produce rich client-side user experiences. The individual technologies that compose AJAX are not recent developments; they have been around for some time and have been continuously updated and improved. However, it is the recent confluence of these technologies that is leading to interesting possibilities.

AJAX News Desk 12/23/05 10:42:12 AM EST

In the past few months, the design pattern of combining Asynchronous JavaScript and XML (AJAX) to develop highly interactive Web applications has been growing in popularity. High-profile Web applications such as Google Maps and A9 are currently leveraging the combination of these technologies to produce rich client-side user experiences. The individual technologies that compose AJAX are not recent developments; they have been around for some time and have been continuously updated and improved. However, it is the recent confluence of these technologies that is leading to interesting possibilities.

Mike 11/14/05 02:21:56 PM EST

I am interested in Geo fencing...would any of the above technologies enable the development of a Google map which has geo fencing capabilities?

Thanks for any input,

Mike

News Desk 10/20/05 11:17:56 PM EDT

Google Maps! AJAX-Style Web Development Using ASP.NET. In the past few months, the design pattern of combining Asynchronous JavaScript and XML (AJAX) to develop highly interactive Web applications has been growing in popularity. High-profile Web applications such as Google Maps and A9 are currently leveraging the combination of these technologies to produce rich client-side user experiences. The individual technologies that compose AJAX are not recent developments; they have been around for some time and have been continuously updated and improved. However, it is the recent confluence of these technologies that is leading to interesting possibilities.

.NET News Desk 09/08/05 12:58:07 PM EDT

AJAX-Style Web Development Using ASP.NET
In the past few months, the design pattern of combining Asynchronous JavaScript and XML (AJAX) to develop highly interactive Web applications has been growing in popularity. High-profile Web applications such as Google Maps and A9 are currently leveraging the combination of these technologies to produce rich client-side user experiences. The individual technologies that compose AJAX are not recent developments; they have been around for some time and have been continuously updated and improved. However, it is the recent confluence of these technologies that is leading to interesting possibilities.

Mark Petersen 09/07/05 10:22:23 AM EDT

The AJAX.NET URL is not correct.

I believe what you are looking for is:
http://ajax.schwarz-interactive.de/csharpsample/default.aspx

This library works in ASP.NET 1.1 as well.

@CloudExpo Stories
"MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
Vulnerability management is vital for large companies that need to secure containers across thousands of hosts, but many struggle to understand how exposed they are when they discover a new high security vulnerability. In his session at 21st Cloud Expo, John Morello, CTO of Twistlock, addressed this pressing concern by introducing the concept of the “Vulnerability Risk Tree API,” which brings all the data together in a simple REST endpoint, allowing companies to easily grasp the severity of the ...
Agile has finally jumped the technology shark, expanding outside the software world. Enterprises are now increasingly adopting Agile practices across their organizations in order to successfully navigate the disruptive waters that threaten to drown them. In our quest for establishing change as a core competency in our organizations, this business-centric notion of Agile is an essential component of Agile Digital Transformation. In the years since the publication of the Agile Manifesto, the conn...
In his session at 21st Cloud Expo, James Henry, Co-CEO/CTO of Calgary Scientific Inc., introduced you to the challenges, solutions and benefits of training AI systems to solve visual problems with an emphasis on improving AIs with continuous training in the field. He explored applications in several industries and discussed technologies that allow the deployment of advanced visualization solutions to the cloud.
Enterprises are adopting Kubernetes to accelerate the development and the delivery of cloud-native applications. However, sharing a Kubernetes cluster between members of the same team can be challenging. And, sharing clusters across multiple teams is even harder. Kubernetes offers several constructs to help implement segmentation and isolation. However, these primitives can be complex to understand and apply. As a result, it’s becoming common for enterprises to end up with several clusters. Thi...
While some developers care passionately about how data centers and clouds are architected, for most, it is only the end result that matters. To the majority of companies, technology exists to solve a business problem, and only delivers value when it is solving that problem. 2017 brings the mainstream adoption of containers for production workloads. In his session at 21st Cloud Expo, Ben McCormack, VP of Operations at Evernote, discussed how data centers of the future will be managed, how the p...
"NetApp is known as a data management leader but we do a lot more than just data management on-prem with the data centers of our customers. We're also big in the hybrid cloud," explained Wes Talbert, Principal Architect at NetApp, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"Space Monkey by Vivent Smart Home is a product that is a distributed cloud-based edge storage network. Vivent Smart Home, our parent company, is a smart home provider that places a lot of hard drives across homes in North America," explained JT Olds, Director of Engineering, and Brandon Crowfeather, Product Manager, at Vivint Smart Home, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
The question before companies today is not whether to become intelligent, it’s a question of how and how fast. The key is to adopt and deploy an intelligent application strategy while simultaneously preparing to scale that intelligence. In her session at 21st Cloud Expo, Sangeeta Chakraborty, Chief Customer Officer at Ayasdi, provided a tactical framework to become a truly intelligent enterprise, including how to identify the right applications for AI, how to build a Center of Excellence to oper...
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
"Infoblox does DNS, DHCP and IP address management for not only enterprise networks but cloud networks as well. Customers are looking for a single platform that can extend not only in their private enterprise environment but private cloud, public cloud, tracking all the IP space and everything that is going on in that environment," explained Steve Salo, Principal Systems Engineer at Infoblox, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventio...
Large industrial manufacturing organizations are adopting the agile principles of cloud software companies. The industrial manufacturing development process has not scaled over time. Now that design CAD teams are geographically distributed, centralizing their work is key. With large multi-gigabyte projects, outdated tools have stifled industrial team agility, time-to-market milestones, and impacted P&L stakeholders.
"ZeroStack is a startup in Silicon Valley. We're solving a very interesting problem around bringing public cloud convenience with private cloud control for enterprises and mid-size companies," explained Kamesh Pemmaraju, VP of Product Management at ZeroStack, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"We're focused on how to get some of the attributes that you would expect from an Amazon, Azure, Google, and doing that on-prem. We believe today that you can actually get those types of things done with certain architectures available in the market today," explained Steve Conner, VP of Sales at Cloudistics, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"Codigm is based on the cloud and we are here to explore marketing opportunities in America. Our mission is to make an ecosystem of the SW environment that anyone can understand, learn, teach, and develop the SW on the cloud," explained Sung Tae Ryu, CEO of Codigm, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Data scientists must access high-performance computing resources across a wide-area network. To achieve cloud-based HPC visualization, researchers must transfer datasets and visualization results efficiently. HPC clusters now compute GPU-accelerated visualization in the cloud cluster. To efficiently display results remotely, a high-performance, low-latency protocol transfers the display from the cluster to a remote desktop. Further, tools to easily mount remote datasets and efficiently transfer...
High-velocity engineering teams are applying not only continuous delivery processes, but also lessons in experimentation from established leaders like Amazon, Netflix, and Facebook. These companies have made experimentation a foundation for their release processes, allowing them to try out major feature releases and redesigns within smaller groups before making them broadly available. In his session at 21st Cloud Expo, Brian Lucas, Senior Staff Engineer at Optimizely, discussed how by using ne...
Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...