Hi, if I am writing a web custom control, do I override the Render method or
the RenderControl or the RenderContents method - and what is the difference?

Thanks,
Peter

Hi,

basically the chain goes so that at render stage, Page calls into
RenderControl of your control, which again directs this call to Render and
that again to again RenderContents. Does your control have RenderContents
depends on if it derives directly from System.Web.UI.WebControls.WebControl.

Essentially the main Render methods are:

System.Web.UI.Control
=================

-RenderControl
-Render
-RenderChildren

They are implemented so that RenderControl calls Render if control is
visible. Render then calls directly RenderChildren which calls RenderCotrol
for every child control

System.Web.UI.WebControl
====================

-derives from System.Web.UI.Control so has inherited Control's rendering
methods

Adds following rendering methods to the implementation:

-AddAttributesToRender
-RenderBeginTag
-RenderContents
-RenderEndTag

And what's important, WebControl overrides Render method pretty much like
this

protected override void Render(HtmlTextWriter writer)
{
    RenderBeginTag(writer);
    RenderContents(writer);
    RenderEndTag(writer);
}

where RenderBeginTag calls  AddAttributesToRender and writes out the begin
tag by using given HtmlTextWriter. And WebControl's RenderContents calls to
base.Render which essentially of course calls Control's Render methods
causing child controls to be rendered.

So what's this all about? It's tight set of predefined rendering flow in
which you can override everything or just one small snippet of it.
Therefore what you want to render is the driving reason to think what should
be overridden and when. Difference with the methods you asked is pretty much
that with RenderControl you make the control to render at any time as
RenderControl is also a public method. Render and RenderContents are
protected methods only callable in the class or in derived classes. Render
is meant to control the entire rendering flow while RenderContents is meant
to render markup between control's begin and end tags.

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