Page 210:Page object calling a private method from BasePage?

aperture8 · August 2nd, 2010, 03:23 AM

Note "Private Sub Page_PreRender" is a private method. How does the derived Page Class manage to call this private method? BTW the book is excellent and crammed with info.

Imar · August 2nd, 2010, 03:26 AM

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How does the derived Page Class manage to call this private method?

It doesn't. It's the BasePage class itself that executes this code. Or in fact, it's the parent Page class that raises the event which is then handled by BasePage.

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BTW the book is excellent and crammed with info.

Thank you. Spread the word, Spread the word.... ;-)

Cheers,

Imar

aperture8 · August 2nd, 2010, 03:45 AM

Hi Imaar,

Thanks for the reply.

Do you mean when (say) Default.aspx object is created, it's constructor calls the base page's constructor, which raises the Page.PreRender event and so the the code is executed?

You don't put this code in the master page because masterpage is suited to handle common layout but BasePage is suited to handle common programming logic?

If you have a bit of time, can you tell me how to best understand inheritance? As when you call an inherited method MethodA() in the derived class, does it actually creates a base class object and pass the call to the base class's MethodA()? So even private methods are inherited becasue the derived object just pass the call to the base class method?

I'm gonna write good reviews on Amazon after I finish reading the whole book. Cheers.

Imar · August 2nd, 2010, 04:03 AM

Hi there,

Quote:

Do you mean when (say) Default.aspx object is created, it's constructor calls the base page's constructor, which raises the Page.PreRender event and so the the code is executed?

The other way around. When the child class is created, first the base constructor is called, then its own. You may want to read more about this here:

http://www.codeproject.com/KB/dotnet...sInCSharp.aspx
http://www.blackwasp.co.uk/ConstructorInheritance.aspx
http://aspalliance.com/770
http://www.yoda.arachsys.com/csharp/constructors.html
http://blogs.msdn.com/b/ericlippert/...-part-one.aspx
http://blogs.msdn.com/b/ericlippert/...-part-two.aspx

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You don't put this code in the master page because masterpage is suited to handle common layout but BasePage is suited to handle common programming logic?

TYes, that's how I typically handle it. You can mix and match if you want, but I find that separating logic and design like this makes a lot of sense.

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As when you call an inherited method MethodA() in the derived class, does it actually creates a base class object and pass the call to the base class's MethodA()? So even private methods are inherited becasue the derived object just pass the call to the base class method?

Not, not really. it doesn't create the base class, it *is* the base class, plus more. Think animals, for example. A dog is an animal, so when you create a dog you actually create an animal of type dog. The dog itself doesn't create an animal, it *is* an animal.

So, when you have this:

public class Dog : Animal {... }

and then construct a dog like this:

Dog myDog = new Dog();

Then first the Animal's constructor is called.

To see what I mean, put breakpoints in your code such as in the BasePage class and then debug (see Chapter 18). Then you can see the order of events.

Cheers,

Imar

btcomp · August 8th, 2010, 10:20 PM

Wow, some pretty heavy stuff, and an hour before I retire for the night. I was searching chapter 6 threads for more info and was glad to read it. I had just written in the book margins to go over the pages 210-214. I do understand much of this better, but I think that as I am reading ahead a bit to use the Master pages, to learn the design techniques for a template.

I think it is a great lesson in Base Pages and Inheritance. I think writing some classes while I am learning the basics of ASP.NET will help. I am thinking of putting up a couple of metric to English pages on my website, since I am on a Dieting forum with people in Australia, England, Europe and Canada and we are weighing in kilograms and pounds. I'm always telling the temperature in Michigan in Fahrenheit and then converting it longhand on paper to Celsius, so I am going to add this to my website at www.bdtcomp.com and maybe at the same time make a master page of my current design which is a combination of PHP and CSS. So in effect I'm killing two birds with one stone. (bad analogy because I love my animals, because we have a yellow lab and two yellow cats.)

The importance of this base page, so far is a great way to force you to put titles on all your web pages, something that I forget to do too often!

Imar · August 9th, 2010, 02:25 AM

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The importance of this base page, so far is a great way to force you to put titles on all your web pages,

Yes, but that's only one of its uses....

Imar

btcomp · August 9th, 2010, 07:04 AM

I agree, it's my starting point with the base page. I've bookmarked this link to look at as I learn more. http://www.codeguru.com/csharp/.net/...cle.php/c11939