Beginning ASP.NET 4.5 in CSharp and VB Opsylum

572 x CHAPTER 15 WORKING WITH DATA — ADVANCED TOPICS
How It Works
Although short, this exercise demonstrates a powerful way to hook into the different events of a control
and change the presentation of the underlying control. To see how it works, take a look at the modified
SQL code first:
SELECT
Genre.Id, Genre.Name, Genre.SortOrder, COUNT(Review.Id) AS NumberOfReviews
FROM
Genre LEFT OUTER JOIN
Review ON Genre.Id = Review.GenreId
GROUP BY
Genre.Id, Genre.Name, Genre.SortOrder
This modified SQL statement gets all the columns from
the Genre table but introduces a new column, called
NumberOfReviews, which contains the number of reviews
associated with each genre. It does this by executing the SQL
COUNT function against the Id column of the Review table.
The statement uses GROUP BY to group the selected rows into a
set of summary rows by collapsing non-unique rows. Because
the SQL statement is grouped on all unique columns in the
Genre table, you get a unique row including the number of
reviews for each genre row, whether or not reviews are associated,
as shown in Figure 15-9, which displays the result of this
query in SSMS.
When this query is executed, the GridView in the markup of FIGURE 15-9
the page makes use of the first three columns, just as it did in
the previous version of this page. But you can access the fourth column as well. You do this in the Code
Behind, in the RowDataBound event to be exact, which fires for each row after the GridView is done
binding the data for a specific row:
VB.NET
Protected Sub GridView1_RowDataBound(sender As Object,
e As GridViewRowEventArgs) Handles GridView1.RowDataBound
Select Case e.Row.RowType
Case DataControlRowType.DataRow
...
End Select
End Sub
C#
protected void GridView1_RowDataBound (object sender, GridViewRowEventArgs e)
{
switch (e.Row.RowType)
{
case DataControlRowType.DataRow:
...
}
}