Re: Namespaces - broad question
From: Random (cipherlad_at_hotmail.com)
Date: 04/08/04
- Next message: Bob: "Re: Using one instance of SqlConnection in an ASP.NET page"
- Previous message: Alex Papadimoulis: "Re: Equiv of a CRON job?"
- In reply to: Kevin Spencer: "Re: Namespaces - broad question"
- Next in thread: Kevin Spencer: "Re: Namespaces - broad question"
- Reply: Kevin Spencer: "Re: Namespaces - broad question"
- Messages sorted by: [ date ] [ thread ]
Date: Thu, 8 Apr 2004 13:45:41 -0700
hoo, boy. What a thread this is turning out to be. First, I do understand,
and you have confirmed a lot of things I have suspected.
Let me take a different approach on this, if I may. Let's say I have two
aspx pages that I know I want utilize a specific function within, that is
contained in a class. Without having to copy/paste this function into a
different class in a different codebehind page (because I don't want them to
have the same codebehind page), how can I reference this function.
NONE of the tutorials or materials I have read go beyond a one page example.
Seperation of code and HTML... fine. It's the sharing of code through
namespaces and classes that I'm having difficulty grasping at this point.
"Kevin Spencer" <uce@ftc.gov> wrote in message
news:%23ZasEUaHEHA.308@tk2msftngp13.phx.gbl...
> Hi Random,
>
> > I realize that while Visual Studio automatically encourages a 1 to 1
> > relationship between aspx and codebehind pages, this does not
necessarily
> > need to be the case. I also realize that errors would occur during
> > compiling if the same class was written in different places. What I
don't
> > understand is how Visual Studio keeps track in the assembly of where all
> > these written classes are?
>
> A .Net assembly is a compiled DLL. The data in the code files is compiled
> into binary code in the DLL, including all the namespace information,
> references, etc. Once compiled into a DLL, your CodeBehind class files are
> nothing but dead weight. They are not used; the DLL is. So, forget about
the
> "written classes". Think about the classes themselves, rather than the
code
> you write to create them.
>
> > As another example, what if I wrote an aspx page that inherited a class
> > contained in a codebehind page that was NOT referenced by the aspx page?
>
> You wouldn't be able to compile OR use it. An aspx Page is a composite of
2
> distinct entities: the Page Template (.aspx) and the CodeBehind class. The
> Page Template inherits the CodeBehind class, which inherits
> System.Web.UI.Page. The .aspx file by itself can do nothing without
> CodeBehind, whether that is in the same (.aspx) file as the Page Template,
a
> CodeBehind file, or a DLL. The important thing is that the .aspx Page
> Template has a reference in it telling it where to look for the class
> definition that it inherits. If the CodeBehind is compiled into a DLL, and
> that DLL is in one of the locations that ASP.Net can find it (Global
> Assembly Cache or \bin folder), ASP.Net uses Reflection to query the
> assembly for the class, based upon the NameSpace and Class name of the
> class. All of this information is contained in the DLL itself.
>
> > Since the class is found in the assembly, how would the aspx page know
> where
> > to look? When the code is all compiled, does it automatically all the
> > classes available from a central source? And if this is the case,
> wouldn't
> > it make more sense to put all the code into a *.vb or *.cs file where it
> can
> > be centrally referenced?
>
> Again, only the CodeBehind is compiled. The Page Template (.aspx) must
have
> a Reference in it telling it where to find the CodeBehind class. There IS
> not "central source" for information about .Net classes. That is why you
can
> simply put your DLLs into the \bin folder of your web app, and they will
be
> found. Once found, the .Net platform can query the DLLs to find the DLL
> needed, and the class inside the DLL to use.
>
> Take a look at the following example, from an ASPX page I created:
>
> <%@ Page Language="vb" AutoEventWireup="false"
> Codebehind="WebForm1.aspx.vb" Inherits="ControlTest.WebForm1"%>
>
> The "CodeBehind" attribute is there solely for the benefit of Visual
> Studio.Net. It tells VS.Net what file to compile to create the DLL used by
> the Page class(es). The "Inherits" directive is the key. Note that it
> contains no information about the location of the DLL. ASP.Net KNOWS where
> the DLL can be located. Instead, it contains a reference to a NameSpace
and
> a class, which it can find by using Reflection on the assemblies in the
\bin
> folder and the GAC.
>
> --
> HTH,
> Kevin Spencer
> .Net Developer
> Microsoft MVP
> Big things are made up
> of lots of little things.
>
> "Random" <cipherlad@hotmail.com> wrote in message
> news:#DVrHZZHEHA.2624@TK2MSFTNGP10.phx.gbl...
> > I know you are not trying to offend, Marina, but I am an experienced
> > programmer, just new to .NET, and I have read a lot, from the basics. I
> am
> > disappointed that a lot of the 'beginner' material has been unhelpful
when
> > it comes to an architectural overview of ASP.NET, which is what I am
> trying
> > to clarify here. I thought that by asking 'basic' questions, I might
get
> a
> > better understanding of how things fit into the whole. So please be
> patient
> > with me in this.
> >
> > I realize that while Visual Studio automatically encourages a 1 to 1
> > relationship between aspx and codebehind pages, this does not
necessarily
> > need to be the case. I also realize that errors would occur during
> > compiling if the same class was written in different places. What I
don't
> > understand is how Visual Studio keeps track in the assembly of where all
> > these written classes are?
> >
> > As another example, what if I wrote an aspx page that inherited a class
> > contained in a codebehind page that was NOT referenced by the aspx page?
> > Since the class is found in the assembly, how would the aspx page know
> where
> > to look? When the code is all compiled, does it automatically all the
> > classes available from a central source? And if this is the case,
> wouldn't
> > it make more sense to put all the code into a *.vb or *.cs file where it
> can
> > be centrally referenced?
> >
> > You are right, I think there is something very simple I am
> misunderstanding,
> > but for the life of me, I can't locate the answer anwhere.
> >
> > Random
> >
> > "Marina" <someone@nospam.com> wrote in message
> > news:e7UIi%23YHEHA.4032@TK2MSFTNGP12.phx.gbl...
> > > I have no idea what you are talking about to be honest.
> > >
> > > The class is already in a namespace - the Inherits attribute is just
> > > referencing. It isn't creating a new namespace or a new class. So I
> have
> > no
> > > idea what you are talking about when you ask about namespaces being
> > written
> > > in central locations.
> > >
> > > You can have any number of pages inherit from the same class - as long
> as
> > > that class actually exists. In the visual studio model, you would have
> to
> > > manually do that, because it assume a 1 to 1 ration between pages and
> code
> > > behind classes.
> > >
> > > If you tried to compiled two classes with the same name into the same
> > > assembly, the compiler would not allow you to do this. The assembly
> > itself
> > > knows what classes it has, and what namespace each one is in, in it's
> > > manifest.
> > >
> > > I would recommend you start at the very basics of ASP.NET, it sounds
> like
> > > you are missing some basic concept about how this all works. In your
> > first
> > > post you asked about the difference between a namespace and a class -
so
> > it
> > > seems like you need to go to the beginning of .NET, and not just into
> the
> > > middle of ASP.NET.
> > >
> > > "Random" <cipherlad@hotmail.com> wrote in message
> > > news:uau2myYHEHA.3032@TK2MSFTNGP09.phx.gbl...
> > > > Okay, that clarifies the "Inherits" vs. "Imports" question very
well.
> > > > Thanks.
> > > >
> > > > As far as the namespace being available in the assembly, though, let
> me
> > > give
> > > > you an example...
> > > >
> > > > Using the portal code I gave before, would I be able to write
another
> > aspx
> > > > page, use the same "Inherits=<fully qualified class name>" phrasing,
> > > without
> > > > that class being written into the different codebehind page
referenced
> > in
> > > > the new aspx page?
> > > >
> > > > If yes, why? Shouldn't namespaces be written in a more centrally
> > > referenced
> > > > file?
> > > >
> > > > If no, then how can the assembly keep track of all the declared
> > > namespaces?
> > > > And what would it do if two or more codebehind references had the
same
> > > > namespace and class written in them?
> > > >
> > > > Random
> > > >
> > > > "Marina" <someone@nospam.com> wrote in message
> > > > news:eqT6TmYHEHA.2668@TK2MSFTNGP10.phx.gbl...
> > > > > This inherits attribute, refers to the name of the class this page
> > > > inherits
> > > > > from. The class's name is CDefault, but it is located in the
> > > > > ASPNET.StarterKit.Portal namespace, and so the namespace has to
> > preceed
> > > > it.
> > > > >
> > > > > At runtime, asp.net looks for a class with the name in the
inherits
> > > > > attribute.
> > > > >
> > > > > This has nothing to do with projects, or namespaces being
available.
> > It
> > > is
> > > > > just the fully qualified name of the class.
> > > > >
> > > > > "Random" <cipherlad@hotmail.com> wrote in message
> > > > > news:OI$efeYHEHA.548@TK2MSFTNGP09.phx.gbl...
> > > > > > Hmm. I'm trying to teach myself from examples and tutorials and
> > > books.
> > > > > > Specifically in this case, I'm trying to learn from the MS
> > > > > PortalStarterKit.
> > > > > > Specifically, the default page in that example has as the first
> line
> > > in
> > > > > > default.aspx:
> > > > > >
> > > > > > <%@ Page CodeBehind="Default.aspx.vb" language="vb"
> > > > > AutoEventWireup="false"
> > > > > > Inherits="ASPNET.StarterKit.Portal.CDefault" %>
> > > > > >
> > > > > > The codebehind page has:
> > > > > >
> > > > > > Namespace ASPNET.StarterKit.Portal
> > > > > > Public Class CDefault
> > > > > > Inherits System.Web.UI.Page
> > > > > > Private Sub Page_Load(ByVal sender As System.Object,
ByVal
> e
> > > As
> > > > > > System.EventArgs) Handles MyBase.Load
> > > > > > <code here>
> > > > > > End Sub
> > > > > > End Class
> > > > > > End Namespace
> > > > > >
> > > > > > I'm trying to find out how and why this works the way that it
> does.
> > > > It's
> > > > > > more complex than the examples given by tutorials and books.
> > > > > >
> > > > > > And again, I'm trying to figure out how the namespace declared
> here
> > > > makes
> > > > > > it's way into the assembly. And because it does, somehow, does
> that
> > > > make
> > > > > it
> > > > > > available through the entire project?
> > > > > >
> > > > > > Random
> > > > > >
> > > > > > "Marina" <someone@nospam.com> wrote in message
> > > > > > news:%23WIkSAYHEHA.2260@TK2MSFTNGP09.phx.gbl...
> > > > > > > First of all, namespaces can be used with the 'Imports'
keyword,
> > so
> > > as
> > > > > not
> > > > > > > have to write out the full namespace for every class, not the
> > > > 'Inherits'
> > > > > > > attribute.
> > > > > > >
> > > > > > > Think of namespaces as folders in your file system, and
classes
> as
> > > the
> > > > > > files
> > > > > > > in them. So a namespace itself isn't anything but an
> > organizational
> > > > > > > container for classes - just as a folder is just a container
for
> > > > files.
> > > > > > > Classes are the actual things that you instantiate, and call
> > methods
> > > > on.
> > > > > > >
> > > > > > > I didn't really understand your questions. I think they all
stem
> > > from
> > > > > not
> > > > > > > understanding what a namespace actually is.
> > > > > > >
> > > > > > > "Random" <cipherlad@hotmail.com> wrote in message
> > > > > > > news:uD4r44XHEHA.2668@TK2MSFTNGP10.phx.gbl...
> > > > > > > > I'm confused about the proper use and usefulness of
> namespaces.
> > I
> > > > > > beleive
> > > > > > > I
> > > > > > > > understand the purpose is so the developer can put classes
> > within
> > > > > > > namespaces
> > > > > > > > to essentially organize your code. And I understand that
you
> > > > declare
> > > > > > your
> > > > > > > > intention to use a namespace within a page through the
> > "Inherits"
> > > > > > > attribute.
> > > > > > > > I know that using "Inherits" isn't absolutely necessary,
it's
> > just
> > > > > > > > recommended so the developer doesn't have to type out the
> entire
> > > > > > namespace
> > > > > > > > in code. I know that namespaces have to appear in the
project
> > > > > assembly,
> > > > > > > > however...
> > > > > > > >
> > > > > > > > How does the assembly find a namespace that the developer
has
> > > > > > written????
> > > > > > > > In all the examples I've seen, namespaces have been written
in
> > > > > > codebehind
> > > > > > > > pages. How does this make them accessible to the entire
> > project?
> > > > > > What's
> > > > > > > to
> > > > > > > > prevent a duplicate namespace from being written in a
> different
> > > > > > codebehind
> > > > > > > > page? Is there a better place to write all the project
> > namespaces
> > > > for
> > > > > > > more
> > > > > > > > centralized accessibility?
> > > > > > > >
> > > > > > > > And finally, how do namespaces DIFFER from classes?
> > > > > > > >
> > > > > > > > Random
> > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> >
> >
>
>
- Next message: Bob: "Re: Using one instance of SqlConnection in an ASP.NET page"
- Previous message: Alex Papadimoulis: "Re: Equiv of a CRON job?"
- In reply to: Kevin Spencer: "Re: Namespaces - broad question"
- Next in thread: Kevin Spencer: "Re: Namespaces - broad question"
- Reply: Kevin Spencer: "Re: Namespaces - broad question"
- Messages sorted by: [ date ] [ thread ]
Relevant Pages
|
