HtmlSelect.OnServerChange(EventArgs) 方法
定义
重要
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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 -> unitProtected Overridable Sub OnServerChange (e As EventArgs)参数
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
另请参阅
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