GridView Control in ASP.NET - Part 9
Working with GridView Control Events
The GridView control includes a rich set of events that we can handle
to customize the control's behavior and appearance. These events can be divided
into three groups.
First, the GridView control supports
the following set of events that are raised when the control displays its rows:
· DataBinding Raised
immediately before the GridView is bound to its
data source.
· DataBound Raised
immediately after a GridView is bound to its data source.
· RowCreated Raised
when each row in the GridView is created.
· RowDataBound Raised
when each row in the GridView is bound to data.
Second, the GridView control
includes the following set of events that are raised when we are editing
records:
· RowCommand Raised
when an event is raised by a control contained in the GridView.
· RowUpdating Raised
immediately before a GridView updates a record.
· RowUpdated Raised
immediately after a GridView updates a record.
· RowDeleting Raised
immediately before a GridView deletes a record.
· RowDeleted Raised
immediately after a GridView deletes a record.
· RowCancelingEdit Raised
when we cancel updating a record.
Finally, the GridView control
supports the following events related to sorting, selecting, and paging:
· PageIndexChanging Raised
immediately before the current page is changed.
· PageIndexChanged Raised
immediately after the current page is changed.
· Sorting Raised
immediately before sorting.
· SelectedIndexChanging Raised
immediately before a row is selected.
· SelectedIndexChanged Raised
immediately after a row is selected.
Using Highlighting GridView Rows
Introduction & Demonstration
Imagine that we want to highlight particular rows in a GridView. For
example, when displaying a table of marks totals, we might want to highlight
the rows in which the marks are greater than a certain amount.
<%@ Page Language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
If e.Row.RowType = DataControlRowType.DataRow Then
Dim TOTAL_MARKS As Decimal = CType(DataBinder.Eval(e.Row.DataItem, "TOTAL_MARKS"), Decimal)
If TOTAL_MARKS >
450 Then
e.Row.BackColor
= System.Drawing.Color.Blue
End If
End If
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title></title>
<style type="text/css">
</style>
</head>
<body>
<form id="form1" runat="server" >
<div>
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
DataSourceID="SqlDataSource1"
EmptyDataText="There are no data
records to display." Width="262px" OnRowDataBound="GridView1_RowDataBound">
<Columns>
<asp:BoundField DataField="ID" HeaderText="ID" SortExpression="ID" />
<asp:BoundField DataField="NAME" HeaderText="NAME" SortExpression="NAME" />
<asp:BoundField DataField="TOTAL_MARKS" HeaderText="TOTAL_MARKS (out
of 500)"
SortExpression="TOTAL_MARKS" />
</Columns>
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:DatabaseConnectionString1 %>"
ProviderName="<%$ ConnectionStrings:DatabaseConnectionString1.ProviderName %>"
SelectCommand="SELECT [ID],
[NAME], [TOTAL_MARKS] FROM [MARKSHEET]">
</asp:SqlDataSource>
</div>
</form>
</body>
</html>
In above figure, the GridView1_RowDataBound() method
is executed when the GridView renders each of its
rows. The second parameter passed to this event handler is an instance of the GridViewRowEventArgs class.
This class exposes a GridViewRow object that represents
the row being bound.
The GridViewRow object supports several useful
properties, here is some of them:
· Cells Represents
the collection of table row cells associated with the row being bound.
· DataItem Represents
the data item associated with the row being bound.
· DataItemIndex Represents
the index of the data item in its DataSet associated with the row being bound.
· RowIndex Represents
the index of the row being bound.
· RowState Represents
the state of the row being bound. Possible values are Alternate, Normal, Selected, Edit.
Because these values can be combined (for example, the RowState can
be Alternate Edit), use a bitwise comparison with RowState.
· RowType Represents
the type of row being bound. Possible values are DataRow, Footer, Header, NullRow, Pager, Separator.
In above list, the RowType property
we have used to verify that the row is a DataRow. The DataItem property
is used to retrieve the database record associated with the row. Notice that
the DataBinder.Eval() method is used to
retrieve the value of the TOTAL_MARKS.
Note: Continue in Next Part.
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