HtmlTextArea.OnServerChange(EventArgs) Method

Reference

Definition

Namespace:: System.Web.UI.HtmlControls

Assembly:: System.Web.dll

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.

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

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)

Parameters

e: EventArgs

A EventArgs that contains the event data.

Examples

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="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="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>

<%@ 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>

Remarks

The ServerChange event is raised when the content of the HtmlTextArea control changes between posts to the server.

Note

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.

Note

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 Handling and Raising Events.

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(EventArgs) in a derived class, be sure to call the base class's OnServerChange(EventArgs) method so that registered delegates receive the event.

Applies to