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HtmlTextArea.OnServerChange Method

Raises the ServerChange event of the HtmlTextArea control. This allows you to provide a custom handler for the event.

Namespace:  System.Web.UI.HtmlControls
Assembly:  System.Web (in System.Web.dll)

protected virtual void OnServerChange(
	EventArgs e
)

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.

NoteNote:

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.

NoteNote:

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 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="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 Server_Change(Object sender, EventArgs e)
  {

    // 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)
      Span1.InnerHtml = "Your comment cannot exceed 20 characters.";
    else
      Span1.InnerHtml = "You wrote: <br />" + TextArea1.Value;

  }

</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="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 Server_Change(Object sender, EventArgs e)
  {
    // 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)
    {
      Span1.InnerHtml = "Your comment cannot exceed 20 characters.";
    }
    else
    {
      Span1.InnerHtml = "You wrote: <br />" + TextArea1.Value;
    }

  }

  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.
    TextArea1.ServerChange +=
      new System.EventHandler(this.Server_Change);

  }

</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>

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
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