Listview With Group Headers in ASP.Net

Let's say we want to implement a ListView with group headers, where each group is defined by a certain data column having the same value. In other words, each time the data column has a new value (proceeding from top to bottom), we want to have a special view that highlights that fact.

The ListView control renders its ItemTemplate once for every item in its DataSource. As discussed in Grouping Data with the ListView Control, it is possible to insert a grouping template for every N records. This flexibility allows for scenarios like displaying data in a multi-column table. While the built-in grouping feature is certainly useful when it comes to displaying data most people think of grouping to mean that records with similar attributes are lumped together. For instance, the Ticket Booking database contains information about an assortment of products, and each product has attributes like PNR_NUMBER, NAME, MOBILE_NO, BOOKED_BY, BOARDING_POINT, FARE, and so forth. While each NAME name is unique, many PNR_NO share the same Boarding point and BoardingPointTime. When someone says, "I want to group the PNR_NUMBER data," usually they mean they want to group it by one of these common attributes. The following screenshot shows the user interface people most people associate with the term grouping. Unfortunately, the ListView's grouping feature does not allow for this style of grouping. The good news is that with a few lines of code and markup we can construct such an interface. This article shows how to build a flexible grouping interface that allows the user to choose what data field to group the data by. Read on to learn more!

By adding the preceding databinding syntax we are instructing the ListView to call the AddGroupingRowIfBoardingHasChanged() each time it renders the ItemTemplate, that it will do once per record being bound to the ListView. The AddGroupingRowIfBoardingHasChanged() method, which we will create momentarily, will return either an empty string (in the case that the supplier name hasn't changed since the last product) or the HTML for a table row that announces the new BoardingPoint. Next, create the AddGroupingRowIfBoardingHasChanged() method in the page's code-behind class. This method must return a string value and canont be marked Private (that is, it must be marked as Public or Protected). Keep in mind that this method is called once for every record being bound to the ListView. Add the following code: