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Headlines for 4GuysFromRolla.com. 4Guys is an online resource site for ASP and ASP.NET information!

Locking the Screen During a PostbackDecember 16 2008

In a perfect world all web applications would be snappy and responsive, and there would be no such thing as lengthy postback waits. But in the real world there are plenty of scenarios that take seconds to complete. For example, when a user visits a travel booking site like Expedia and enters his origination and destination information, it's not unusual for it to take several seconds before the search results appear. Similarly, I've worked on applications where clicking a button dynamically generated and e-mailed a large PDF file, or that have needed to query a very slow database located in corporate offices halfway around the world. In such cases it was not uncommon for the user to have to wait several seconds between submitting the form and getting a response from the web server.

While browsers provide some feedback to the user that the form has been submitted and a response is forthcoming, these visual cues are usually in the margins of the browser and still allow the user to interact with the page, re-click the button, or interact with some other user interface element on the page. Most travel sites send the user to a "Please Wait While We Process Your Results..."-type page when they submit their query. This does two things: it provides the user with visual feedback that their submission was accepted, and it prohibits them from re-submitting their search query twice.

You can mimic "Please Wait While We Process Your Results..." functionality in a single

Key Configuration Settings When Deploying a Web ApplicationDecember 9 2008

The configuration information for an ASP.NET application is stored in one or more XML-based configuration files named Web.config. The default configuration settings for all web applications on the web server are spelled out in the Web.config file in the $WINDOWS$\Microsoft.NET\Framework\version\CONFIG folder. These default settings can be added to over overridden for a specific web application by the Web.config file in that application's root directory. Moreover, these configuration settings can be customized for a web application on a folder-by-folder basis by adding Web.config files to the application's subfolders.

The Web.config file spells out an array of configuration settings, including: database connection strings, authentication and URL authorization rules, and the behavior that unfolds when an unhandled exception occurs, among many others. Many configuration settings differ between the development environment and the production environment. For example, when you are developing an ASP.NET application on your desktop you are likely using a different database than when the application is in production. Consequently, the database connection strings in Web.config need to be updated when deploying an application.

Some of these types of configuration settings must be changed when deploying an application, like database connection strings. Failure to modify the configuration information when deploying will cause the web application not to

Modifying the HTTP Response Using FiltersDecember 2 2008

When a browser requests an ASP.NET page from a web server, the ASP.NET engine takes that request through a number of steps that, together, generate the resulting markup, which is returned to the requesting browser for display. The stages in this process are referred to as the HTTP Pipeline and perform tasks like authentication, authorization, and having the requested page render its content. During one of the later stages in the HTTP Pipeline the rendered markup is handed off to a response filter which, if supplied, has an opportunity to inspect and modify the markup before it is returned to the requesting browser.

With a little bit of code you can create your own response filters and associate them with a particular page, a particular type of page (such as ASP.NET resources that generate HTML), or for all ASP.NET resources. And if you are using IIS 7's integrated mode you can have your filter work with the output of any content type. This article provides an overview of response filters and shows two such filters: a naive filter that strips out whitespace to reduce the size of the markup sent over the wire, and a filter that adds a copyright message to the bottom of all web pages. You can download these two filters, along with a simple demo application, at the end of this article, with examples in both C# and Visual Basic.

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Creating Charts with the Google Chart APINovember 18 2008

I've always wondered how the phrase "A picture is worth a thousand words" came about. I like to think that it was coined by some mid-level manager viewing a sales figures report that consisted of metrics from the past 1,000 days. After scanning this long list of numbers, he found, at the bottom of the page, a line chart that summarized the numbers, and uttered that now well-known adage. Charts and graphs provide a succinct synopsis of large amounts of data. With charts a person can quickly spot trends, compare different resultsets, or recognize patterns.

There are many ways to create charts in an ASP.NET web page. You can use the classes in the System.Drawing namespace to programmatically generate charts; you can use the Microsoft Office Web Components (OWC). There are also open-sourcecharting tools and a plethora of third-party components, as well. Microsoft has even entered the game and introduced

Examining ASP.NET 2.0's Membership, Roles, and Profile - Part 13October 21 2008

ASP.NET's forms-based authentication system in tandem with the Membership API and Login Web controls make it a cinch to create a user store, create user accounts, and allow visitors to log into the site. What's more, with little effort it's possible to define roles, associate user accounts with roles, and determine what functionality is available based on the currently logged in user's role (see Part 2). Many ASP.NET sites that use Membership have an Admin role, and users in that role are granted certain functionality not available to non-Admin users. Consider an online store - Admin users might be able to manage inventory, whereas the only way normal members could interact with the inventory was by adding items to their shopping cart.

I was recently working with a client who had an interesting request: he needed the ability for Admin users to be able to log into the site as another user, and perform actions as if that other person had logged in herself. Returning to the online store example, imagine that some customers periodically phone in their order, or mail or fax in an order form. An Admin, receiving this order, could then log into the site as that customer and place the order on the customer's behalf.

This article shows how to allow an Admin user to log into a Membership-based website as another user, and includes a complete working demo available for download at the end of the ar