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Over the past several years web developers have started using JavaScript to make asynchronous postbacks to the web server that only transmit and receive the necessary data; these techniques are commonly referred to as AJAX. When properly implemented, AJAX-enabled web applications offer a highly interactive user interface whose responsiveness rivals that of desktop applications. Popular web applications like the social networking news site Digg and GMail are prime examples of AJAX techniques in action.

Since AJAX involves many disparate technologies at different layers in the networking stack, implementing AJAX without the use of an AJAX framework is difficult and error-prone. Fortunately, Microsoft has released a free AJAX framework for ASP.NET developers: Microsoft ASP.NET AJAX. This article is the first in a series of articles that examines the ASP.NET AJAX framework. This installment provides an overview of AJAX technologies and looks at getting started with Microsoft"s framework. Future installments will focus on specific controls and scenarios. Read on to learn more!
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Many independent developers and small companies building Internet-accessible web applications turn to web hosting companies to host their website. Web hosting companies offer a variety of plans, from dedicated servers to shared plans. Shared plans, which are the most economical and practical for low-traffic websites, can have anywhere from 25 to 150 separated websites hosted from the same web server. When hosting multiple websites on the same server, it is important that one website cannot affect or harm another site. For example, both the web hosting company and its (honest) customers want to prevent one website from, say, reading the connect string information from Web.config of another website.

ASP.NET allows for web hosting companies to define trust levels, which dictate what operations are permitted by ASP.NET applications. A web hosting company can either use one of the preset trust levels - Full, High, Medium, Low, or Minimal - or can create a custom trust level. Full turst, which is the default, allows ASP.NET applications to execute native code, to read from the Registry and Windows Event Log, and to read and write to files outside of the application"s virtual directory. In short, with full trust one web application could delete the entire contents of another web application!

Fortunately, most web hosting companies run in medium trust, which greatly reduces the potential for harm by limiting the set of operations an ASP.NET application can perform. While the protection granted by medium trust is reassuring, its limited functionality can be aggrevating for honest developers. In this article we"ll look at how the trust-level is specified, what functionality is limited by medium trust, and some techniques to work around these limitations. Read on to learn more!
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The .NET Framework makes creating and consuming Web Services a walk in the park. Creating a Web Service is as easy as marking a class with the WebService attribute; Web Services can be easily consumed because the .NET Framework includes tools to build proxy classes given a Web Service"s WSDL file. All of the examples we have seen in previous installments in this article series have consumed Web Services from server-side code. That is, a Web Service is consumed when a postback occurs and server-side code in an ASP.NET page creates an instance of the proxy class and invokes one of its methods.

In 2007 Microsoft released their free ASP.NET AJAX framework, which simplifies building AJAX-enabled ASP.NET applications (see An Introduction to AJAX and Atlas with ASP.NET 2.0 for more information). The ASP.NET AJAX framework is best known for its myriad of AJAX-enabled Web controls, but it also includes functionality to create and consume Web Services through client-side script. Best of all, the workflow for creating script-accessible Web Services is very similar to creating Web Services consumed through server-side .NET code. To mark a Web Service as being consumable from client script, simply add the ScriptService attribute; the service can be consumed through script via an auto-generated JavaScript proxy class.

In this article we"ll look at how to use Microsoft"s ASP.NET AJAX framework to consume Web Services from script. We will also examine how the low-level communication differs between Web Services consumed from .NET code versus Web Services consumed from JavaScript. Read on to learn more!
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As web developers, we most often focus on backend web developer, buring our noses in defining and implementing the business logic, building CRUDs, and designing reports. Rarely are we concerned about maintaining the appearance and style of the website. For developers working in medium- to large-sized companies, this poses no problem as there are graphic designers whose job it is to design a slick layout and periodically update it in order to keep the site from becoming stale. In smaller companies, however, oftentimes the web developer writing the backend code is also the one responsible for maintaining the frontend.

One easy and cost-effective way of keeping a site from becoming stale is to display different images on a page each time it is visited. Many corporate websites use this technique on their homepages. For example, the homepage might have a picture of a facility or employees in the upper right hand corner. Rather than showing a single, static picture, each time the homepage is visited a randomly selected image is displayed.

There are a couple of ways to display random images, and this article will look at two different approaches. The first technique covered in this article is to simply display a randomly selected image file from a directory of files. This simplistic approach is easy to implement but is limited in a number of ways. We"ll also look at a more professional approach that utilizes a free, open-source ContentRotator control I created back in September 2005. With the my ContentRotator control where you can specify what images, exactly, are candidates for being displayed as well as how likely a particular image should be selected relative to the other images in the image set. Read on to learn more!
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ASP.NET 2.0"s Membership, Roles, and Profile systems were designed using the provider model, which enables these systems to seamlessly use different implementations. ASP.NET ships with a provider for managing members and roles through SQL Server and another for using Active Directory. It is also possible to plug in other implementations that have been built from the ground up or downloaded from other sources. For example, you can download alternative providers from Microsoft that store membership and role information in a Microsoft Access database (see Part 8 of this article series). Most of the articles in this series, however, have focused on using the SQL Server provider (SqlMembershipProvider, SqlRoleProvider, and SqlProfileProvider). The SQL Server providers are typically the provider of choice for Internet-based web applications, whereas the Active Directory providers are more commonly used in intranet scenarios.

The SQL Server providers create a number of tables, views, and stored procedures in the specified SQL Server database. Therefore when using these providers it is possible to add, modify, or delete membership or roles or profile-related data through T-SQL statements. In this article we"ll look at a common membership need - deleting users. While users can certainly be deleted through the .NET Membership API, there are scenarios where it may be much easier to use a T-SQL script. However, bypassing the managed APIs and working directly with the database is not without its own host of challenges. By the end of this article we"ll have addressed these issues, discussed the pros and cons of using T-SQL in lieu of the managed APIs, and have examined both the managed API methods and T-SQL commands for deleting a single user and deleting all users. Read on to learn more!
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The polling User Control examined in the first two installments (Design Decisions and the Data Model and Building the Polling User Control) is functionally complete at this point. A page developer can add, edit, or delete new polls and poll answers by manually inserting, updating, or deleting records into or from the corresponding database tables; they can view a poll"s results by running a query against the UserResponses table.

Having to work directly with the database in terms of SELECT, INSERT, UPDATE, and DELETE queries can be a pain, of course, especially for commonly performed techniques. A more palatable option is to provide a web-based interface for these common tasks. The download available at the end of each installment of this article series includes, in addition to the polling User Control, a set of administration web pages that make it easy to create, edit, and delete polls and poll questions and to view the results of any poll in the system.

In this third and final installment we"ll examine these three administration pages" functionality, declarative markup, and code. Read on to learn more!
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Welcome to the second article in a three-part series on building a polling User Control. In the first installment, Design Decisions and the Data Model, we looked at the design decisions made prior to creating the control as well as the poll"s data model, which consisted of three tables in a SQL Server 2005 database.

We are now ready to start building the poll"s user interface. Since my poll control only allows authenticated users to vote, if an anonymous visitor reaches the poll or if the authenticated user has already voted then the User Control displays the results of the poll in a read-only interface. If visited by an authenticated user who has yet to take the poll, it allows the user to vote, after which the results are stored in the database and the results displayed to the user.

In addition to building the polling User Control, we"ll also look at how to add the poll to a web page. Read on to learn more!
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Many websites include some sort of polling user interface through which visitors can cast their vote on the topic du jour. The typical polling user interface includes some question text, like "What is your favorite programming language?", along with a series of radio buttons listing possible answers, like "C#", "Visual Basic", "Pascal", and so forth. The visitor can select an answer and then cast his vote. After voting, the interface changes to show the current voting breakdown per answer, as the screen shots below illustrate.

This article is the first in a three-part series that examines how to build a data-driven reusable polling User Control. In this first part we"ll look at the design decisions made in creating this control as well as the polling data model. The second installment will step through the process of building the polling user interface while the third and final installment will examine the administration portion. Read on to learn more!
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ASP.NET 2.0"s data source and data Web controls make working with data much easier than in previous versions by allowing for a declarative approach to working with data. In short, the data source controls make it possible to retrieve, insert, update, and delete data without having to write the tedious dedata access code that was so commonplace in ASP.NET version 1.x. (A previous installment of this article series examined using the SqlDataSource to insert data into a database.)

In this article we will focus on using the SqlDataSource control to delete records from a database. Specifically, we will look at three examples: using a SqlDataSource and a bit of server-side code to delete a record selected from a drop-down list; and using the GridView Web control"s built-in deleting support; and how to programmatically cancel a delete operation. Read on to learn more!
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Displaying data in ASP.NET verison 1.x required writing code to programmatically retrieve the data and then more code to bind the data to a data Web control, such as the DataGrid. ASP.NET 2.0 simplifies the process of working with data through its data source controls, which allow data to be retrieved and even modified through declarative means. In short, ASP.NET 2.0"s data source controls permit developers to work with and display data without having to write a line of code. For a more thorough look at working with data in ASP.NET 2.0, be sure to check out my Accessing and Updating Data in ASP.NET 2.0 article series.

Different data source controls are designed to work with different types of data. The XmlDataSource control, as its name implies, is designed for working with XML data. By setting a few properties, it is possible to retrieve XML data from a remote URL or local file, transform it using XSLT, and filter it using an XPath expression, all without writing a line of code. This data can then be displayed by binding it to a data Web control and XPath databinding statements can be used to bind specific chunks of the resulting XML to other Web controls.

In this article we will see just how easy it is to display XML data in an ASP.NET 2.0 page. In particular, we will build a User Control that will display the contents of an RSS feed. Once created, this User Control can be dragged onto the Design surface of any ASP.NET page in your project and configured to display the contents of a particular RSS feed by simply setting the control"s Url property to the URL of the RSS feed. Read on to learn more!
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