HtmlTextArea.OnServerChange Method (EventArgs)
Raises the ServerChange event of the HtmlTextArea control. This allows you to provide a custom handler for the event.
Assembly: System.Web (in System.Web.dll)
Parameters
- e
-
Type:
System.EventArgs
A System.EventArgs that contains the event data.
The ServerChange event is raised when the content of the HtmlTextArea control changes between posts to the server.
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This event is only raised when the user initiates a post to the server, such as by clicking a submit button. This event does not cause a post to the server to occur. |
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The control must have viewstate enabled for the ServerChange event to work correctly. |
This event is commonly used to perform data validation on the HtmlTextArea control when the user updates the text in the control.
Raising an event invokes the event handler through a delegate. For more information, see NIB: Raising an Event.
The OnServerChange method also allows derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.
Notes to Inheritors:
When overriding OnServerChange in a derived class, be sure to call the base class's OnServerChange method so that registered delegates receive the event.
The following code example demonstrates how to specify and create a custom event handler for the ServerChange event. A message is displayed when the value entered in the HtmlTextArea control exceeds 20 characters.
<%@ 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 Server_Change(ByVal sender As Object, ByVal e As EventArgs) ' The ServerChange event is commonly used for data validation. ' This method determines whether the comment entered into the ' HtmlTextArea control is longer than 20 characters. If TextArea1.Value.Length > 20 Then Span1.InnerHtml = "Your comment cannot exceed 20 characters." Else Span1.InnerHtml = "You wrote: <br />" + TextArea1.Value End If End Sub </script> <html xmlns="http://www.w3.org/1999/xhtml" > <head> <title>HtmlTextArea ServerChange Example</title> </head> <body> <form id="form1" runat="server"> <h3>HtmlTextArea ServerChange Example</h3> Enter your comments: <br /> <textarea rows="2" cols="20" id="TextArea1" onserverchange="Server_Change" runat="server"/> <br /> <input type="submit" value="Submit" runat="server"/> <br /> <span id="Span1" 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 Server_Change(ByVal sender As Object, ByVal e As EventArgs) ' The ServerChange event is commonly used for data validation. ' This method determines whether the comment entered into the ' HtmlTextArea control is longer than 20 characters. If TextArea1.Value.Length > 20 Then Span1.InnerHtml = "Your comment cannot exceed 20 characters." Else Span1.InnerHtml = "You wrote: <br />" + TextArea1.Value End If End Sub Sub Page_Load(ByVal sender As Object, ByVal 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 TextArea1.ServerChange, AddressOf Server_Change End Sub </script> <html xmlns="http://www.w3.org/1999/xhtml" > <head> <title>HtmlTextArea ServerChange Example</title> </head> <body> <form id="form1" runat="server"> <h3>HtmlTextArea ServerChange Example</h3> Enter your comments (20 or fewer characters): <br /> <textarea rows="2" cols="20" id="TextArea1" runat="server"/> <br /> <input type="submit" value="Submit" runat="server"/> <br /> <span id="Span1" runat="server" /> </form> </body> </html>
Available since 1.1
