In the last two installments of this article series - Updating Basics and Customizing the Editing Interface - we saw how to configure the SqlDataSource control to issue UPDATE statements to a database and how to then configure the GridView control to work in tandem with the SqlDataSource control to provide a web-based editing interface. By default, the GridView's editing interface renders a TextBox for each editable column in the grid. However, in certain scenarios we may want to customize the editing interface by including validation controls or by using an alternative Web control to collect the user's input. In particular, we customized the editing interface so that when editing a product from the Northwind database, a user could select the product's category through a DropDownList control rather than having to enter the actual CategoryID value into a TextBox.

While the Customizing the Editing Interface article provided a complete, working example of creating a customized editing interface, it had one potentially criticial shortcoming - the approach did not work with products that had a NULL database value for their CategoryID. For starters, the SELECT query used to populate the GridView used an INNER JOIN, which only returned those products with a matching category record. But even if we update the query to use a LEFT JOIN, the DropDownList in the customized editing interface did not include a list item representing the NULL value, so a user would be unable to edit a product and change the category from an existing value to NULL.

In this article we will look at how to customize the DropDownList in the editing interface such that it can correctly handle database NULL values. Read on to learn more!
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On November 19, 2007, Microsoft officially released the ASP.NET version 3.5 and Visual Studio 2008. Like with the progression from ASP.NET 2.0 to 3.0, the features in ASP.NET 3.5 are additive, meaning that the core assemblies installed from the .NET Framework version 2.0 are still used by the 3.0 and 3.5 versions. The In short, ASP.NET 3.5 doesn't change or take away or break any functionality, concepts, or code present in 2.0 - it simply adds new types and features and capabilities to the framework.

Visual Studio 2008 is the recommended tool for developing ASP.NET applications. Unlike previous versions of Visual Studio, which were targeted to a specific framework version (i.e., Visual Studio .NET 2003 targeted ASP.NET 1.1 and Visual Studio 2005 targeted ASP.NET 2.0), Visual Studio 2008 is multi-targeted, meaning that you choose from a drop-down list whether to have Visual Studio 2008 build applications against the ASP.NET 2.0, 3.0, or 3.5 frameworks. Visual Studio 2008 also includes an improved Designer experience, JavaScript debugging and IntelliSense features, and the ability to view and even step into the core .NET Framework code during debugging.

This article provides an overview of the new features in ASP.NET 3.5 and the new web/ASP.NET-related features in Visual Studio 2008. Read on to learn more!
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ASP.NET 2.0 added a number of built-in client-side enhancements that were missing from earlier versions. Many of these new features were detailed in an earlier article here on 4Guys, Client-Side Enhancements in ASP.NET 2.0. One of the least undocumented yet most helpful client-side enhancement, in my opinion, is MaintainScrollPositionOnPostback.

As its name implies, MaintainScrollPositionOnPostback ensures that the browser's scroll position is maintained across postbacks. Without MaintainScrollPositionOnPostback, when a user visits a web page that is "taller" than the browser window, they have to scroll down to see the content further down on the page. If the user then clicks on a Button or performs some other action that causes a postback, the browser reloads the page and, by default, returns to the home scroll position at the top of the page, requiring the user to scroll back down to the location they were viewing when the postback occurred. To have the user's scroll position remembered across postbacks, simply set MaintainScrollPositionOnPostback to True, which can be done on a page-by-page basis or applied to all pages by configuring this option through Web.config.

While MaintainScrollPositionOnPostback makes it easy to keep the visitor at the same scroll position across postbacks, there are scenarios where you may not want to return the user to their scroll position on postback, but instead return them to the top of the page. One such example is when displaying a pageable grid. When the user edits a record, you would want to keep them at the same scroll position, but when they change the page or delete a record, you may want to reset their scroll position to the top on postback. In this article we will examine a way to override the behavior of MaintainScrollPositionOnPostback on a case-by-case basis. Read on to learn more!
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