HtmlSelect.OnServerChange(EventArgs) 方法

參考

定義

命名空間:: System.Web.UI.HtmlControls

組件:: System.Web.dll

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

引發 ServerChange 控制項的 HtmlSelect 事件。這個方法可讓您提供該事件的自訂處理常式。

protected:
 virtual void OnServerChange(EventArgs ^ e);

protected virtual void OnServerChange (EventArgs e);

abstract member OnServerChange : EventArgs -> unit
override this.OnServerChange : EventArgs -> unit

Protected Overridable Sub OnServerChange (e As EventArgs)

參數

e: EventArgs

EventArgs，其中包含事件資料。

範例

下列程式碼範例示範如何為控制項的事件 HtmlSelect 指定和撰寫事件處理常式 ServerChange 的程式碼。事件處理常式會判斷選取的專案是否彼此相容。

<%@ Page Language="C#" AutoEventWireup="True" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">

    void Button_Click (Object sender, EventArgs e)
    {
        Label1.Text = "You selected:";

        for (int i=0; i<=Select1.Items.Count - 1; i++)
        {
           if (Select1.Items[i].Selected)
               Label1.Text += "<br />    -" + Select1.Items[i].Text;      
        }

    }

    void Server_Change (Object sender, EventArgs e)
    {
        int Count = 0;

        for (int i=0; i<=Select1.Items.Count - 1; i++)
        {
           if (Select1.Items[i].Selected)
               Count++;      
        }

        if ((Count > 1) && (Select1.Items[0].Selected))
            Label2.Text = "Hey! You can't select 'All' with another selection!!";
        else
            Label2.Text = "";
    }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title> HtmlSelect Example </title>
</head>

<body>

   <form id="form1" runat="server">

      <h3> HtmlSelect Example </h3>

      Select items from the list: <br /><br />

      <select id="Select1" 
              multiple="true"
              onserverchange="Server_Change"
              runat="server">

         <option value="All"> All </option>
         <option value="1" selected="selected"> Item 1 </option>
         <option value="2"> Item 2 </option>
         <option value="3"> Item 3 </option>
         <option value="4"> Item 4 </option>
         <option value="5"> Item 5 </option>
         <option value="6"> Item 6 </option>

      </select>

      <br /><br />

      <button id="Button1"
              onserverclick="Button_Click"
              runat="server">

         Submit

      </button>

      <br /><br />

      <asp:Label id="Label1"
           runat="server"/>

      <br />

      <asp:Label id="Label2"
           runat="server"/>

   </form>

</body>

</html>

<%@ Page Language="VB" AutoEventWireup="True" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">

    Sub Button_Click (sender As Object, e As EventArgs)
        Dim i As Integer

        Label1.Text = "You selected:"
        For i = 0 to Select1.Items.Count - 1
           If Select1.Items(i).Selected Then
               Label1.Text = Label1.Text & "<br />    -" & Select1.Items(i).Text
           End If         
        Next
    End Sub

    Sub Server_Change (sender As Object, e As EventArgs)
        Dim i As Integer
        Dim Count As Integer = 0

        For i = 0 to Select1.Items.Count - 1
            If Select1.Items(i).Selected Then
                Count = Count + 1
            End If         
        Next

        If Count > 1 And Select1.Items(0).Selected Then
            Label2.Text = "Hey! You can't select 'All' with another selection!!"
        Else
            Label2.Text = ""
        End If
    End Sub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title> HtmlSelect Example </title>
</head>
<body>
<form id="form1" runat="server">
   <div>

      <h3> HtmlSelect Example </h3>

      Select items from the list: <br /><br />

      <select id="Select1" 
              multiple="true"
              onserverchange="Server_Change"
              runat="server">

         <option value="All"> All </option>
         <option value="1" selected="selected"> Item 1 </option>
         <option value="2"> Item 2 </option>
         <option value="3"> Item 3 </option>
         <option value="4"> Item 4 </option>
         <option value="5"> Item 5 </option>
         <option value="6"> Item 6 </option>

      </select>

      <br /><br />

      <button id="Button1"
              onserverclick="Button_Click"
              runat="server">

         Submit

      </button>

      <br /><br />

      <asp:Label id="Label1"
           runat="server"/>

      <br />

      <asp:Label id="Label2" runat="server"/>

   </div>
</form>
</body>
</html>


<%@ Page Language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">
    void Button_Click (Object sender, EventArgs e)
    {
        // Display the selected items.
        Label1.Text = "You selected:";

        for (int i=0; i<=Select1.Items.Count - 1; i++)
        {
            if (Select1.Items[i].Selected)
                Label1.Text += "<br />    -" + Select1.Items[i].Text;      
        }
    }

    void Server_Change(Object sender, EventArgs e)
    {
        // The ServerChange event is commonly used for data validation.
        // This method will display a warning if the "All" option is  
        // selected in combination with another item in the list.
        int Count = 0;

        // Determine the number of selected items in the list.
        for (int i=0; i<=Select1.Items.Count - 1; i++)
        {
            if (Select1.Items[i].Selected)
                Count++;      
        }

        // Display an error message if more than one item is selected with
        // the "All" item selected.
        if ((Count > 1) && (Select1.Items[0].Selected))
            Label2.Text = "Hey! You can't select 'All' with another selection!!";
        else
            Label2.Text = "";
    }

    void Page_Load(Object sender, EventArgs e)
    {
        // Create an EventHandler delegate for the method you want to
        // handle the event, and then add it to the list of methods
        // called when the event is raised.
        Select1.ServerChange += new System.EventHandler(this.Server_Change);
        Button1.ServerClick += new System.EventHandler(this.Button_Click);
    }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title> HtmlSelect Server Change Example </title>
</head>
<body>
<form id="form1" runat="server">
   <div>

      <h3> HtmlSelect Server Change Example </h3>

      Select items from the list: <br /><br />

      <select id="Select1" 
              multiple="true"
              runat="server">

         <option value="All"> All </option>
         <option value="1" selected="selected"> Item 1 </option>
         <option value="2"> Item 2 </option>
         <option value="3"> Item 3 </option>
         <option value="4"> Item 4 </option>
         <option value="5"> Item 5 </option>
         <option value="6"> Item 6 </option>

      </select>

      <br /><br />

      <button id="Button1"
              runat="server">

         Submit

      </button>

      <br /><br />

      <asp:Label id="Label1"
           runat="server"/>

      <br />

      <asp:Label id="Label2"
           runat="server"/>

   </div>
</form>
</body>
</html>


<%@ 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">

    Sub Button_Click (sender As Object, e As EventArgs)
        ' Display the selected items.
        Label1.Text = "You selected:"

        Dim i As Integer

        For i=0 To Select1.Items.Count - 1
            If Select1.Items(i).Selected Then
                Label1.Text &= "<br />    -" & Select1.Items(i).Text
            End If      
        Next
    End Sub

    Sub Server_Change(sender As Object, e As EventArgs)
        ' The ServerChange event is commonly used for data validation.
        ' This method will display a warning if the "All" option is 
        ' selected in combination with another item in the list.
        Dim Count As Integer = 0
        Dim i As Integer

        ' Determine the number of selected items in the list.
        For i=0 To Select1.Items.Count - 1
            If Select1.Items(i).Selected Then
                Count = Count + 1      
            End If
        Next

        ' Display an error message if more than one item is selected with
        ' the "All" item selected.
        If ((Count > 1) And (Select1.Items(0).Selected)) Then
            Label2.Text = "Hey! You can't select 'All' with another selection!!"
        Else
            Label2.Text = ""
        End If
    End Sub

    Sub Page_Load(sender As Object, e As EventArgs)
        ' Create an EventHandler delegate for the method you want to 
        ' handle the event, and then add it to the list of methods
        ' called when the event is raised.
        AddHandler Select1.ServerChange, AddressOf Server_Change
        AddHandler Button1.ServerClick, AddressOf Button_Click
    End Sub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title> HtmlSelect ServerChange Example </title>
</head>
<body>
<form id="form1" runat="server">
   <div>

      <h3> HtmlSelect ServerChange Example </h3>

      Select items from the list: <br /><br />

      <select id="Select1" 
              multiple="true"
              runat="server">

         <option value="All"> All </option>
         <option value="1" selected="selected"> Item 1 </option>
         <option value="2"> Item 2 </option>
         <option value="3"> Item 3 </option>
         <option value="4"> Item 4 </option>
         <option value="5"> Item 5 </option>
         <option value="6"> Item 6 </option>

      </select>

      <br /><br />

      <button id="Button1"
              runat="server">

         Submit

      </button>

      <br /><br />

      <asp:Label id="Label1"
           runat="server"/>

      <br />

      <asp:Label id="Label2"
           runat="server"/>

   </div>
</form>
</body>
</html>

備註

ServerChange當控制項中 HtmlSelect 選取的專案在貼文到伺服器之間變更時，就會引發事件。

注意

只有在使用者起始張貼至伺服器時，才會引發此事件，例如按一下 [提交] 按鈕。此事件不會造成伺服器張貼。

注意

控制項必須啟用檢視狀態， ServerChange 事件才能正常運作。

當使用者變更控制項中的選取範圍時，您可以使用這個事件對控制項執行資料驗證 HtmlSelect 。

引發事件會透過委派叫用此事件處理常式。如需詳細資訊，請參閱處理和引發事件。

OnServerChange 方法也允許衍生類別處理事件，而不用附加委派。這是在衍生類別中處理事件的慣用技巧。

給繼承者的注意事項

在 OnServerChange(EventArgs) 衍生類別中覆寫方法時，請務必呼叫基類的 OnServerChange(EventArgs) 方法，讓已註冊的委派接收事件。

適用於

共用方式為

HtmlSelect.OnServerChange(EventArgs) 方法

定義

參數

範例

備註

給繼承者的注意事項

適用於

另請參閱

其他資源