"Page.IsValid cannot be called" occurs in Page_PreRender event handler

I'm currently learning ASP.NET, and read that the page validation occurs after Page.Load(). When I put if (Page.IsValid == true) whatever;

then I get an error, even though that line is in my Page_PreRender() event handler.

How does that make sense?

Thanks in advance, just trying to under开发者_如何学JAVAstand it fully.

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You either have to have a control that causes validation doing the postback (CausesValidation="true") or actually call Page.Validate() manually for Page.IsValid to be accessible...otherwise validation hasn't happened, so there's just nothing to check, the value would be meaningless, which is the current error you're seeing.

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The solution does work, I was having problem in OnPageIndexChanging event I used below code

  protected void gvRequests_OnPageIndexChanging(object sender, GridViewPageEventArgs e)
  {
            Page.Validate();
            gvMyRequest.PageIndex = e.NewPageIndex;
            Populate();
  }