ASP.NET:使用DataTable對象儲存資料

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上載者:User
asp.net|對象|資料   DataSet對象是資料表的集合(DataTables),在一個DataSet中可以存放多個DataTable。作為資料來源,DataSet可以提供多個資料表,在DataSet中可以進行表的關聯操作工作,同樣,每個DataTable對象也可以作為資料來源。下面這個執行個體示範了DataTable對象如何提供給DropDownList控制項提供資料來源的。

    建立一個Web表單,命名為DataTable_Simple.aspx,添加兩個DropDownList控制項,設計視窗如8.9所示。


圖 8.9 DataTable_Simple.aspx的設計視窗

切換DataTable_Simple.aspx的HTML代碼視窗,HTML代碼如下:
<%@ Page Language="vb" AutoEventWireup="false" Codebehind="DataTable_Simple.aspx.vb" Inherits="Adodotnet.DataTable_Simple"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
 <HEAD>
  <title>利用DataTable儲存資料</title>
  <meta content="Microsoft Visual Studio .NET 7.1" name="GENERATOR">
  <meta content="Visual Basic .NET 7.1" name="CODE_LANGUAGE">
  <meta content="JavaScript" name="vs_defaultClientScript">
  <meta content="http://schemas.microsoft.com/intellisense/ie5" name="vs_targetSchema">
 </HEAD>
 <body MS_POSITIONING="GridLayout">
  <form id="Form1" method="post" runat="server">
   <FONT face="宋體">
    <TABLE id="Table1" cellSpacing="1" cellPadding="1" width="360" border="1" style="WIDTH: 360px; HEIGHT: 75px">
     <TR>
      <TD align="center"><STRONG>利用DataTable儲存資料</STRONG></TD>
     </TR>
     <TR>
      <TD>第 
       <asp:DropDownList id="DropDownList1" runat="server" Width="107px" AutoPostBack="True"></asp:DropDownList>項的項值是-->
       <asp:DropDownList id="DropDownList2" runat="server"></asp:DropDownList></TD>
     </TR>
    </TABLE>
   </FONT>
  </form>
 </body>
</HTML>
查看DataTable_Simple.aspx的邏輯代碼(即DataTable_Simple.aspx.vb檔案),其中邏輯代碼如下:
'--------cdoe begin----------
Public Class DataTable_Simple
    Inherits System.Web.UI.Page

#Region " Web Form設計器產生的程式碼 "

    '該調用是 Web Form設計器所必需的。
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()

    End Sub
    Protected WithEvents DropDownList1 As System.Web.UI.WebControls.DropDownList
    Protected WithEvents DropDownList2 As System.Web.UI.WebControls.DropDownList

    '注意: 以下預留位置聲明是 Web Form設計器所必需的。
    '不要刪除或移動它。
    Private designerPlaceholderDeclaration As System.Object

    Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init
        'CODEGEN: 此方法調用是 Web Form設計器所必需的
        '不要使用代碼編輯器修改它。
        InitializeComponent()
    End Sub

#End Region

    Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        '在此處放置初始化頁的使用者代碼
        If Not Page.IsPostBack Then
            Dim mydt As DataTable
            DropDownList1.DataSource = dt()
            DropDownList1.DataTextField = "id"
            DropDownList1.DataBind()
            DropDownList2.DataSource = dt()
            DropDownList2.DataTextField = "item"
            DropDownList2.DataBind()
        End If
    End Sub
    '產生DataTable對象函數,並產生資料,把資料儲存在DataTable對象中
    Function dt() As DataTable

        ' 定義一個DataTable對象“MyDataTable”,並執行個體化
        Dim myDataTable As DataTable = New DataTable("MyDataTable")

        ' 聲明 DataColumn對象“myDataColumn”和DataRow對象“ myDataRow”
        Dim myDataColumn As DataColumn
        Dim myDataRow As DataRow

        '執行個體化myDataColumn
        myDataColumn = New DataColumn
        myDataColumn.DataType = System.Type.GetType("System.Int32")
        myDataColumn.ColumnName = "id"
        myDataTable.Columns.Add(myDataColumn)

        '執行個體化myDataColumn
        myDataColumn = New DataColumn
        myDataColumn.DataType = Type.GetType("System.String")
        myDataColumn.ColumnName = "item"
        myDataTable.Columns.Add(myDataColumn)

        ' 執行個體化myDataRow並添加到myDataTable中
        Dim i As Integer
        For i = 0 To 10
            myDataRow = myDataTable.NewRow
            myDataRow("id") = i
            myDataRow("item") = "item " & i
            myDataTable.Rows.Add(myDataRow)
        Next i

        ' 返回myDataTable
        Return myDataTable
    End Function

    Private Sub DropDownList1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DropDownList1.SelectedIndexChanged
        DropDownList2.SelectedIndex = DropDownList1.SelectedIndex
    End Sub
End Class
'---------code end-----------
儲存編譯後,DataTable_Simple.aspx運行效果如圖8.10所示。


圖8.10 DataTable_Simple.aspx運行效果



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