To add an event handler for the Sorting event 1. If you are working with a single-file page, switch to Source view and then add the following directives to the top of the code page:

Ads

< % @ Import Namespace="System.Data" % >
< % @ Import Namespace="System.Data.SqlClient" % >

2. Importing the namespaces will make it easier to write the code needed.

3. If the application is using a code-behind page, switch to the code-behind page Default.aspx.cs and add the following lines to the top of the code file, outside the class declaration:

using System.Data;
using System.Data.SqlClient;

4. In the Default.aspx page, switch to Design view, right-click the DropDownList control, and then click Properties.

5. In the Properties window toolbar, click the Events icon, and then double-click SelectedIndexChanged to create a skeleton event handler.

6. Insert the following highlighted code into the event handler.

Click here to view sample code

This code intercepts the SelectedIndexChanged event for DropDownList1 to specify the second sort parameter based on the value selected. Then, it retrieves the sortorder from the Session state and adds the " ASC" or " DESC" to the Sort property for the DataView. Finally, it rebinds the GridView control to the data.

7. Switch to the Default.aspx page and select the DropDownList control.

8. In the Properties window toolbar, click the Events icon, and then double-click Load to create a skeleton event handler.

9. Insert the following highlighted code into the Page_ Load event handler.

Click here to view sample code

10.11.12.13.14.15.16.17.18.Click here to view sample code

This code handles the sorting event of the GridView control to customize the sort functionality of the GridView control. It uses the sorting functionality of the underlying DataView control. It retrieves the DataView control saved in the Session state. Then, it retrieves the sort order value from Session state and adds " ASC" or " DESC" to theSortExpression property passed to the event handler. It saves the new sort order and the SortExpression value in the Session state. Finally, it displays the SortExpression value in a Label control and rebinds the GridView control to the data. The page can now be tested.

2. The GridView control is displayed with StudentId, StudentName, StudentAge, and CourseId columns. Click a column heading to sort by the contents of that column.

Editing the GridView Control Data

The GridView control already contains all the functions necessary for editing data, since the control is abstract and generic. In fact this is the greatest strength of the GridView control over the DataGrid control.

The GridView control uses the assigned data source to edit the data records and the developer will have to add an additional query to the SqlDataSource control for updation of data. The code would be something like the one illustrated below.

updateCommand="UPDATE StudentMaster SET StudentName=@StudentName, StudentAge=@StudentAge WHERE(StudentMaster.StudentID=@StudentId)"

When the AutoGenerateEditButton property is set to true, the GridView displays an additional column. When update is clicked the GridView searches for an appropriate command object on the underlying data source. It fires the rowUpdating event and checks the CanUpdate property of the data source.

Deleting Displayed Records

Deleting records is similar to updating and Editing. The GridView rides on the data source’s ability to perform data operations. The record deletion is enabled by specifying the AutoGenerateDeleteButton to True. The GridView then renders a column of Delete buttons for each row on the GridView. The data source method is passed as a dictionary key filed name/value pair to uniquely identify the row to delete. However, the GridView does not provide any feedback on the operation.

Inserting Records

GridView does not support inserting data against a data source object.

Using Templates

Individual templates can be defined for each field.

Assigning data binding to a control within a template is easy. Besides individually created fields, the GridView control offers two integrated Templates, PageTemplate and NullTemplate. The latter is useful when an assigned data source returns an empty list of data records. A message can be flashed to the user if an empty record set is returned.

The GridView indeed comes with a lot of goodies. Developers are freed from the large volume of code that had to be written. Though the look and feel of the GridView is similar to the DataGrid, it is really very different.

In the next section we shall examine the DetailsView which is a complementary to the GridView in several ways.