ASP.NET 2.0 Cookbook, 2nd Edition

2.10. Sorting Data in Ascending/Descending Order Within a DataGrid

Problem

You are displaying a table of data in a DataGrid, and you want to let the user sort the data and change the sort order by clicking on the column headers.

Solution

Enable the DataGrid control’s sorting features, and add custom coding to support the sorting along with an indication of the current sort column and order.

In the .aspx file, enable the DataGrid control’s sorting features.

In the code-behind class for the page, use the .NET language of your choice to:

1. Create a data-binding method (bindData in our example) that does the following:

   1. Generates the SQL statement required to get the data from the database with an ORDER BY clause based on the value of the sortExpression parameter

   2. Fills a DataTable with the ordered data from the database

   3. Outputs an image indicating the sort column and sort order beside the current sort column heading

2. Call the data-binding method from the Page_Load method (to support the initial display of the grid) and from the event that is fired when the user clicks on a column header (the dgBooks_SortCommand event in our example).

Figure 2-11 shows the appearance of a typical DataGrid sorted by title in ascending order, the information in the first column. Examples 2-26, 2-27 through 2-28 show the .aspx and code-behind files for an example application that produces this result.

Figure 2-11. DataGrid ...