Question

In an asp.net webforms app I have created a base class for my pages to derive from. I have declared the page load method in the base class as so:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    Response.Write("base")
End Sub

Now, in a class that inherits this class, I have used the page load method again:

Protected Shadows Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    Response.Write("descendant")
End Sub

For a reason I do not understand, I am seeing both parent and child get written to the page. Both Page_Load methods are being executed. Why is this? I was under the impression that shadowing or overloading a base class method in a descendant class would essentially hide the base class method. I have searched the internet but I cannot find a concrete explanation as to why this is happening.

Thanks,
JS

Answer 1

The Page_Loadmethod is bound to the Page.Load event. If you add a Page_Load method to your subclass, the framework automatically adds this one as a handler in addition to the one of the base class. The code resulting from the precompiler could look somewhat like this, and therefore both methods are being executed once the Load event fires:

// VB.net (no idea if this really compiles, I'm more into C#)
AddHandler Load, AddressOf BaseClass.PageLoad
AddHandler Load, AddressOf SubClass.PageLoad