在实际的应用中经常会遇到根据其它列计算某一新列的结果，实现这样的功能有两种办法：一个直接使用SQL语句；另外就是在绑定时进行动态添加。第一种方法以前已经介绍过。下面就是第二种方法的具体实现：
AddDataSetColumn.ASPx
<%@ Page Language="<a href="http://dev.21tx.com/language/vb/" target="_blank">VB</a>" AutoEventWireup="false" Codebehind="AddDataSetColumn.aspx.vb"
Inherits="aspx<a href="http://dev.21tx.com/web/" target="_blank">Web</a>.AddDataSetColumn"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<title>AddDataSetColumn</title>
<meta name="GENERATOR" content="Microsoft Visual Studio <a href="http://dev.21tx.com/dotnet/" target="_blank">.net</a> 7.1">
<meta name="CODE_LANGUAGE" content="Visual Basic .NET 7.1">
<meta name="vs_defaultClientScript" content="<a href="http://dev.21tx.com/web/javascript/" target="_blank">JavaScript</a>">
<meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5">
</HEAD>
<body MS_POSITIONING="GridLayout">
<form id="Form1" method="post" runat="server">
<asp:DataGrid id="DataGrid1" runat="server" AutoGenerateColumns="False"
ShowFooter="True" Width="100%">
<HeaderStyle Font-Names="宋体" Font-Bold="True" HorizontalAlign="Center"
ForeColor="Navy" BackColor="LightSalmon"></HeaderStyle>
<FooterStyle BackColor="#FFCCFF"></FooterStyle>
<Columns>
<asp:TemplateColumn HeaderText="订单号">
<ItemTemplate>
<asp:Label ID="OrderID" Runat="server"></asp:Label>
</ItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="产品号">
<ItemTemplate>
<asp:Label ID="ProductID" Runat="server"></asp:Label>
</ItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="单价">
<ItemTemplate>
<asp:Label ID="UnitPrice" Runat="server"></asp:Label>
</ItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="数量">
<ItemTemplate>
<asp:Label ID="Quantity" Runat="server"></asp:Label>
</ItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="折扣">
<ItemTemplate>
<asp:Label ID="Discount" Runat="server"></asp:Label>
</ItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="总计">
<ItemTemplate>
<asp:Label ID="lblTotal" Runat="server"></asp:Label>
</ItemTemplate>
</asp:TemplateColumn>
</Columns>
</asp:DataGrid>
</form>
</body>
</HTML>
AddDataSetColumn.aspx.vb
Imports System.Web.UI.WebControls
Public Class AddDataSetColumn
Inherits System.Web.UI.Page
#Region " Web 窗体设计器生成的代码 "
'该调用是 Web 窗体设计器所必需的。
<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
End Sub
Protected WithEvents DataGrid1 As System.Web.UI.WebControls.DataGrid
'注意: 以下占位符声明是 Web 窗体设计器所必需的。
'不要删除或移动它。
Private designerPlaceholderDeclaration As System.Object
Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init
'CODEGEN: 此方法调用是 Web 窗体设计器所必需的
'不要使用代码编辑器修改它。
InitializeComponent()
End Sub
#End Region
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim strCnn As String = "Data Source=.\NetSDK; Initial Catalog=Northwind;User ID=sa;Password=;"
Dim oCn As New System.Data.SqlClient.SqlConnection(strCnn)
Dim strSql As System.String = "select * from [Order Details]"
Dim ds As System.Data.DataSet = New System.Data.DataSet
oCn.Open()
Dim da As System.Data.SqlClient.SqlDataAdapter = New System.Data.SqlClient.SqlDataAdapter(strSql, oCn)
' 可以直接使用SQL语句实现，这个方法可以直接绑定，不需要用模板即可
' cmd.CommandText = "select *,UnitPrice * Quantity *(1- Discount) as Total from [Order Details]"
' 我们使用另外一种方法，在DataGrid绑定之前为DataSet添加一个列
da.Fill(ds, "DS")
Dim dvwGrid As DataView = ds.Tables(0).DefaultView
DataGrid1.DataSource = dvwGrid
DataGrid1.DataBind()
oCn.Close()
oCn.Dispose()
End Sub
Private Sub DataGrid1_ItemDataBound(ByVal sender As Object, ByVal e As DataGridItemEventArgs) _
Handles DataGrid1.ItemDataBound
Dim elemType As ListItemType = e.Item.ItemType
If (elemType = ListItemType.Item Or elemType = ListItemType.AlternatingItem) Then
'把DataItem转换回DataRowView对象
Dim myDataRowView As DataRowView = CType(e.Item.DataItem, DataRowView)
Dim myDataRow As DataRow = myDataRowView.Row
CType(e.Item.Cells(0).FindControl("OrderID"), Label).Text = myDataRow("OrderID")
CType(e.Item.Cells(1).FindControl("ProductID"), Label).Text = myDataRow("ProductID")
CType(e.Item.Cells(2).FindControl("UnitPrice"), Label).Text = myDataRow("UnitPrice")
CType(e.Item.Cells(3).FindControl("Quantity"), Label).Text = myDataRow("Quantity")
CType(e.Item.Cells(4).FindControl("Discount"), Label).Text = myDataRow("Discount")
Dim dblPrice As Double = Double.Parse(myDataRow("UnitPrice"))
Dim intQuantity As Integer = Int32.Parse(myDataRow("Quantity"))
Dim intDiscount As Double = Double.Parse(myDataRow("Discount"))
Dim nTotal As String = String.Format("{0:C}", dblPrice * (1 - intDiscount) * intQuantity)
CType(e.Item.Cells(5).FindControl("lblTotal"), Label).Text = nTotal
End If
End Sub
End Class
