ListControl.SelectedIndex 屬性

定義

取得或設定清單中選取項目的最低序數索引。Gets or sets the lowest ordinal index of the selected items in the list.

public:
 virtual property int SelectedIndex { int get(); void set(int value); };
[System.ComponentModel.Bindable(true)]
[System.ComponentModel.Browsable(false)]
public virtual int SelectedIndex { get; set; }
[System.ComponentModel.Bindable(true)]
[System.ComponentModel.Browsable(false)]
[System.Web.UI.Themeable(false)]
public virtual int SelectedIndex { get; set; }
[<System.ComponentModel.Bindable(true)>]
[<System.ComponentModel.Browsable(false)>]
member this.SelectedIndex : int with get, set
[<System.ComponentModel.Bindable(true)>]
[<System.ComponentModel.Browsable(false)>]
[<System.Web.UI.Themeable(false)>]
member this.SelectedIndex : int with get, set
Public Overridable Property SelectedIndex As Integer

屬性值

Int32

清單中選取項目的最低序數索引。The lowest ordinal index of the selected items in the list. 預設值為 -1,表示沒有選取任何項目。The default is -1, which indicates that nothing is selected.

屬性

例外狀況

索引設定為小於 -1,或是大於或等於呈現清單當時清單上的項目數目。The index was set to less than -1, or greater than or equal to the number of items on the list at the time the list is rendered.

範例

下列範例示範如何使用 SelectedIndex 來判斷中選取專案的最低索引 CheckBoxListThe following example demonstrates how to use SelectedIndex to determine the lowest index of the selected items in the CheckBoxList.

<%@ Page Language="C#" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
 
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
 <script language="c#" runat="server">
 
    ICollection CreateDataSource() {
       DataTable dt = new DataTable();
       DataRow dr;
 
       dt.Columns.Add(new DataColumn("IntegerValue", typeof(Int32)));
       dt.Columns.Add(new DataColumn("StringValue", typeof(string)));
       dt.Columns.Add(new DataColumn("DateTimeValue", typeof(DateTime)));
       dt.Columns.Add(new DataColumn("BoolValue", typeof(bool)));
       dt.Columns.Add(new DataColumn("CurrencyValue", typeof(double)));
 
       for (int i = 0; i < 9; i++) {
          dr = dt.NewRow();
 
          dr[0] = i;
          dr[1] = "Item " + i.ToString();
          dr[2] = DateTime.Now;
          dr[3] = (i % 2 != 0) ? true : false;
          dr[4] = 1.23 * (i+1);
 
          dt.Rows.Add(dr);
       }
 
       DataView dv = new DataView(dt);
       return dv;
    }
 
    void Page_Load(Object sender, EventArgs e) {
       if (!IsPostBack) {
          CheckBoxList1.DataSource = CreateDataSource();
          CheckBoxList1.DataTextField="StringValue";
          CheckBoxList1.DataValueField="CurrencyValue";
          CheckBoxList1.DataBind();
       }
    }
 
    void Index_Changed(Object sender, EventArgs e) {
 
       Label1.Text = "The index of the first item selected is: " + 
                     CheckBoxList1.SelectedIndex.ToString(); 
 
    }
 
 </script>
 
 <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
 
    <form id="form1" runat="server">
 
       <asp:CheckBoxList id="CheckBoxList1" 
            OnSelectedIndexChanged="Index_Changed"
            AutoPostBack="true"
            runat="server"/>
 
       <br />
 
       <asp:Label id="Label1" runat="server"/>
 
    </form>
 
 </body>
 </html>
 
<%@ Page Language="VB" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
 
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
 <script language="vb" runat="server">

    Function CreateDataSource() As ICollection
        Dim dt As New DataTable()
        Dim dr As DataRow
        
        dt.Columns.Add(New DataColumn("IntegerValue", GetType(Int32)))
        dt.Columns.Add(New DataColumn("StringValue", GetType(String)))
        dt.Columns.Add(New DataColumn("DateTimeValue", GetType(DateTime)))
        dt.Columns.Add(New DataColumn("BoolValue", GetType(Boolean)))
        dt.Columns.Add(New DataColumn("CurrencyValue", GetType(Double)))
        
        Dim i As Integer
        For i = 0 To 8
            dr = dt.NewRow()
            
            dr(0) = i
            dr(1) = "Item " + i.ToString()
            dr(2) = DateTime.Now
            If (i Mod 2) <> 0 Then
                dr(3) = True
            Else
                dr(3) = False
            End If
            dr(4) = 1.23 *(i + 1)
            
            dt.Rows.Add(dr)
        Next i
        
        Dim dv As New DataView(dt)
        Return dv
    End Function

    Sub Page_Load(sender As Object, e As EventArgs)
        If Not IsPostBack Then
            CheckBoxList1.DataSource = CreateDataSource()
            CheckBoxList1.DataTextField = "StringValue"
            CheckBoxList1.DataValueField = "CurrencyValue"
            CheckBoxList1.DataBind()
        End If
    End Sub

    Sub Index_Changed(sender As Object, e As EventArgs)        
        Label1.Text = "The index of the first item selected is: " & _
            CheckBoxList1.SelectedIndex.ToString()
    End Sub
 
 </script>
 
 <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
 
    <form id="form1" runat="server">
 
       <asp:CheckBoxList id="CheckBoxList1" 
            OnSelectedIndexChanged="Index_Changed"
            AutoPostBack="true"
            runat="server"/>
 
       <br />
 
       <asp:Label id="Label1" runat="server"/>
 
    </form>
 
 </body>
 </html>
 

備註

如果清單控制項只允許一個選取專案,請使用這個屬性來判斷清單中目前選取之專案的索引。Use this property to determine the index of the currently selected item in the list if the list control allows only one selection. 如果清單控制項支援多重選取,請使用這個屬性來判斷所選項目的最低索引。If the list control supports multiple selections, use this property to determine the lowest index of the selected items.

SelectedIndex 回傳時,不會特別儲存屬性的值。The value of the SelectedIndex property is not specifically saved on postback. 它會在使用屬性的回傳時還原 SelectedValueIt is restored on postback using the SelectedValue property. 例如,如果 SelectedValue 屬性是4,則在回傳時, SelectedIndex 屬性會設定為 ListItem 屬性為4的物件索引 ValueFor example, if the SelectedValue property is 4, on postback, the SelectedIndex property is set to the index of the ListItem object that has a Value property of 4. 如果有一個以上的 ListItem 物件具有 Value 的屬性為4, Items 就會選取集合中的第一個專案。If more than one ListItem object has a Value property of 4, the first item in the Items collection is selected.

這個屬性無法由佈景主題或樣式表主題設定。This property cannot be set by themes or style sheet themes. 如需詳細資訊,請參閱 ThemeableAttributeASP.NET 主題和外觀For more information, see ThemeableAttribute and ASP.NET Themes and Skins.

適用於

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