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I have a custom control that own a property. Inside this custom control OnInit method, it utilities this property to do some other job.

So in page side, I initialize this custom control and set its property in Page_Init method. But the custom control's Oninit method is called earlier than the Page_Init method, which means I never get the right property value in OnInit method. So what is the right place to set up the custom control's property value from page code behind side?

Thanks

pengruijun
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2 Answers2

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PreInit exists only for the page, so if you need to set something from the page, that can work. Init fires in reverse order, first for the lowest level control, bubbling up to the page to fire last. All other events fire from the page first on down.

If PreInit can work, use it. Otherwise, another workaround is for the property to check if the value is null and has not provided, and if not, it could fire a NeedValue event requiring you to supply it.

HTH.

Brian Mains
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  • So far I still cannot make it work by using the preinit. see my comment to Wyatt. For the second option you provide, i cannot use it because my property can be null. If it null, nothing to do. Otherwise using this property values to filter a result. Anything else suggestion? Thanks – pengruijun Jul 11 '11 at 01:54
  • You could try doing from the custom control: this.Page.PreInit += CustomControl_PreInit; and attach it that way, I think that is supported. The thing about PreInit; some services for ASP.NET are not available, so be careful. My event approach as the workaround definitely will work. – Brian Mains Jul 11 '11 at 02:02
  • sorry, a bit of confuse. where will this code put "this.Page.PreInit += CustomControl_PreInit"? in the custom control Oninit method? And where to set the property value? – pengruijun Jul 11 '11 at 02:15
  • Constructor of the custom control, not sure 100% it would work... What do you mean by "where to set the property value?" You would set it in the event handler. That's why I asked my first question. I'm confused as to who is supposed to set the value, the page or the custom control... – Brian Mains Jul 11 '11 at 02:41
  • My other approach, define a custom event, fire the event when that property has not been set. – Brian Mains Jul 11 '11 at 02:42
  • Update!! Finally, I create a custom children collection property for the custom control. Now I can set up the value from page front side rather than code behind. thanks – pengruijun Jul 11 '11 at 05:53
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Presuming you are on 2.0 or better, there is a PreInit page-level event that is meant for these sorts of things.

If you can't write it directly from there -- some things like your control might not exist -- you could use the HttpContext.Items to stash the value somewhere the control could grab it from. But that is getting real hackish.

Wyatt Barnett
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  • Sorry, I should mention I use this custom control from a user control. I tried to set the property value from Page_PreInit method of user control. It looks like it is never reached during debugging. Is it right to use Page_PreInit from user control code behind? thanks – pengruijun Jul 11 '11 at 01:50