Control.OnPreRender Method (System.Web.UI)

Switch View :
Classic
Lightweight
ScriptFree
.NET Framework Class Library
Control.OnPreRender Method

Updated: April 2009

Raises the PreRender event.

Namespace:  System.Web.UI
Assembly:  System.Web (in System.Web.dll)
Syntax
Visual Basic (Declaration)
Protected Friend Overridable Sub OnPreRender ( _
	e As EventArgs _
)
Visual Basic (Usage)
Dim e As EventArgs

Me.OnPreRender(e)
C#
protected internal virtual void OnPreRender(
	EventArgs e
)
Visual C++
protected public:
virtual void OnPreRender(
	EventArgs^ e
)
JScript
protected internal function OnPreRender(
	e : EventArgs
)

Parameters

e
Type: System.EventArgs
An EventArgs object that contains the event data.
Remarks

ASP.NET calls this method in order to raise the PreRender event. If you are developing a custom control, you can override this method in order to provide additional processing. If you override this method, you typically call the base control's OnPreRender method. If the base control's OnPreRender method is not called, subscribers to the event will not be notified..

Examples
Visual Basic
' Override the OnPreRender method to set _message to
' a default value if it is null.
Protected Overrides Sub OnPreRender(ByVal e As EventArgs)
    MyBase.OnPreRender(e)
    If _message Is Nothing Then
        _message = "Here is some default text."
    End If
End Sub
C#
// Override the OnPreRender method to set _message to
// a default value if it is null.
protected override void OnPreRender(EventArgs e)
{
    base.OnPreRender(e);
    if (_message == null)
        _message = "Here is some default text.";
}
Platforms

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.
Version Information

.NET Framework

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

Reference

Control Class
Control Members
System.Web.UI Namespace
Page

Other Resources

ASP.NET Page Life Cycle Overview
Change History

Date

History

Reason

April 2009

Revised Remarks section and code example to clarify how the method is used.

Customer feedback.
Community Content

Tom Dykstra - MSFT
Sample incomplete and confusing.
Why not just set
_message = "Parent Text was changed by PreRender method";
in the OnPreRender method? Where exactly to you register PreRender_Handler ?

[Tom Dykstra - MSFT] You could do that if you didn't mind overwriting what might already be in _message. As for where to register a handler, see http://msdn.microsoft.com/en-us/library/6w2tb12s.aspx