HtmlSelect.ServerChange Event
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Occurs when the selected items in the HtmlSelect control change between posts to the server.
public:
event EventHandler ^ ServerChange;public event EventHandler ServerChange;member this.ServerChange : EventHandler Public Custom Event ServerChange As EventHandler Event Type
Examples
The following code example demonstrates how to specify and code an event handler declaratively for the ServerChange event of the HtmlSelect control. The event handler determines whether the selected items are compatible with each other.
<%@ 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>
The following code example demonstrates how to specify and code an event handler programmatically for the ServerChange event of the HtmlSelect control. The event handler determines whether the selected items are compatible with each other.
<%@ 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>
Remarks
The ServerChange event is raised when the selected items in the HtmlSelect control change between posts to the server.
Note
The control must have view state enabled for the ServerChange event to work correctly.
For more information about how to handle events, see Handling and Raising Events.
Applies to
See also
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