Control's OnInit Called Even When Attaching It During Parent's OnPreRender?

Mar 11, 2010

My original understanding was that the page lifecycle is run once for all pages and controls under normal circumstances. When I attached a control during a container's OnPreRender, I encountered a situation where the control's OnInit was not called. OK, I considered that a bug in my code and fixed as such, by attaching the control earlier.

But just today, I encountered a situation where OnInit for a control seems to be called after the normal OnInit has been done for everyone else. See stack below. It seems that during the page's PreRender, the control's OnInit is called as it is being dynamically added.

So I just want to confirm exactly what ASP.NET's behavior is? Does it actually keep track of the stage of each control's lifecycle, and upon adding a new control, it will run from the very beginning?

[HttpException (0x80004005): The control collection cannot be modified during DataBind, Init, Load, PreRender or Unload phases.]
System.Web.UI.ControlCollection.Add(Control child) +8678663
MyCompany.Web.Controls.SetStartPageWrapper.OnInit(EventArgs e)
System.Web.UI.Control.InitRecursive(Control namingContainer) +333
System.Web.UI.Control.InitRecursive(Control namingContainer) +210
System.Web.UI.Control.AddedControl(Control control, Int32 index) +198
System.Web.UI.ControlCollection.Add(Control child) +80
MyCompany.Web.Controls.PageHeader.OnPreRender(EventArgs e) in
System.Web.UI.Control.PreRenderRecursiveInternal() +80
System.Web.UI.Control.PreRenderRecursiveInternal() +171
System.Web.UI.Control.PreRenderRecursiveInternal() +171
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +842

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