Visual Basic .NET  

GridView Control in ASP.NET: Part 9

Please you do read earlier parts of this article for complete understanding in GridView.

Part - 8

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.
  • Sorted Raised immediately after 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.

grid9.gif

 <%@ 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 AsGridViewRowEventArgs)
        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.
HAVE A GREAT CODING!

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