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答案：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="vb" AutoEventWireup="false" Codebehind="AddDataSetColumn.<a href=>asp</a>x.vb"Inherits="<a href=>asp</a>xWeb.AddDataSetColumn"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><HTML> <HEAD> <title>AddDataSetColumn</title> <meta name="GENERATOR" content="Microsoft Visual Studio .NET 7.1"> <meta name="CODE_LANGUAGE" content="Visual Basic .NET 7.1"> <meta name="vs_defaultClientScript" content="javascript"> <meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5"> </HEAD> <body MS_POSITIONING="GridLayout"> <form id="Form1" method="post" runat="server"> <<a href=>asp</a>: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> <<a href=>asp</a>:TemplateColumn HeaderText="订单号"> <ItemTemplate> <<a href=>asp</a>:Label ID="OrderID" Runat="server"></<a href=>asp</a>:Label> </ItemTemplate> </<a href=>asp</a>:TemplateColumn> <<a href=>asp</a>:TemplateColumn HeaderText="产品号"> <ItemTemplate> <<a href=>asp</a>:Label ID="ProductID" Runat="server"></<a href=>asp</a>:Label> </ItemTemplate> </<a href=>asp</a>:TemplateColumn> <<a href=>asp</a>:TemplateColumn HeaderText="单价"> <ItemTemplate> <<a href=>asp</a>:Label ID="UnitPrice" Runat="server"></<a href=>asp</a>:Label> </ItemTemplate> </<a href=>asp</a>:TemplateColumn> <<a href=>asp</a>:TemplateColumn HeaderText="数量"> <ItemTemplate> <<a href=>asp</a>:Label ID="Quantity" Runat="server"></<a href=>asp</a>:Label> </ItemTemplate> </<a href=>asp</a>:TemplateColumn> <<a href=>asp</a>:TemplateColumn HeaderText="折扣"> <ItemTemplate> <<a href=>asp</a>:Label ID="Discount" Runat="server"></<a href=>asp</a>:Label> </ItemTemplate> </<a href=>asp</a>:TemplateColumn> <<a href=>asp</a>:TemplateColumn HeaderText="总计"> <ItemTemplate> <<a href=>asp</a>:Label ID="lblTotal" Runat="server"></<a href=>asp</a>:Label> </ItemTemplate> </<a href=>asp</a>:TemplateColumn> </Columns> </<a href=>asp</a>:DataGrid> </form> </body></HTML> AddDataSetColumn.aspx.vb
Imports System.Web.UI.WebControlsPublic 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 SubEnd Class
