HtmlSelect.OnServerChange(EventArgs) 方法

参考

定义

命名空间:: System.Web.UI.HtmlControls

程序集:: System.Web.dll

重要

一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。

引发 HtmlSelect 控件的 ServerChange 事件。这使你可以为事件提供自定义处理程序。

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)

参数

e: EventArgs

包含事件数据的 EventArgs。

示例

下面的代码示例演示如何为 ServerChange 控件的 HtmlSelect 事件指定和编码事件处理程序。事件处理程序确定所选项是否相互兼容。

<%@ 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>

注解

当 ServerChange 控件中的选定项在 HtmlSelect 发布到服务器的帖子之间发生更改时，将引发该事件。

注意

仅当用户向服务器发起帖子（例如单击“提交”按钮）时，才会引发此事件。此事件不会导致发布到服务器。

注意

控件必须启用视图状态， ServerChange 事件才能正常工作。

当用户更改控件中的 HtmlSelect 选择时，可以使用此事件对控件执行数据验证。

引发事件时，将通过委托调用事件处理程序。有关详细信息，请参阅处理和引发事件。

OnServerChange 方法还允许派生类对事件进行处理而不必附加委托。这是在派生类中处理事件的首选技术。

继承者说明

在派生类中重写 OnServerChange(EventArgs) 方法时，请务必调用基类的 OnServerChange(EventArgs) 方法，以便注册的委托接收事件。

适用于

通过

HtmlSelect.OnServerChange(EventArgs) 方法

定义

参数

示例

注解

继承者说明

适用于

另请参阅

其他资源