A dynamic proxy at runtim is certainly not the "preferred way" of
weaving aspects in *ANY* language tht has an intermediate
representation. A "link" time weave would be preferred for many
reasons. The link time weave also helps greatly in mitigating common
issues such as "too much magic". Although has been decided to be a
non-optimal way of doing things, using the profiling API to
uinstrument IL at runtime holds much more possibility of being a good
system than the dynamic proxy.
Cheers,
Greg
On 2/25/07, Frans Bouma <[EMAIL PROTECTED]> wrote:
> On the IL level there are various call* instructions like call, callvirt and
> calli. The former two are the ones which interest us most in this
> discussion. As you probably know, a virtual call has a level of indirection
> through a so-called v-table structure ("method table"), which makes such a
> call more expensive. If you need more information on this, drop a follow-up
> mail or browse the internet or the CLI spec.
>
> As Tony pointed out, Anders Hejlsberg has pointed out the reasons for the
> choice of non-virtual by default on
> http://www.artima.com/intv/nonvirtual.html. Performance and versioning are
> the main reasons as pointed out by Anders.
Still, it's sad this decision was made, because AOP is a tad more
difficult because subclassing at runtime to create dyn. proxies now relies on
the developer to make things virtual, while in Java for example, everything is
virtual by default, so it's more natural: the developer can just write code
and it's weavable at runtime.
dyn. proxy at runtime has many advantages, and because MS doesn't
realize that a dyn. proxy mechanism is really needed in the CLR, all kinds of
tricks have to be used which aren't really transparent. This IMHO limits .NET
when compared to Java.
FB
------------------------------------------------------------------------
Lead developer of LLBLGen Pro, the productive O/R mapper for .NET
LLBLGen Pro website: http://www.llblgen.com
My .NET blog: http://weblogs.asp.net/fbouma
Microsoft MVP (C#)
------------------------------------------------------------------------
>
> -Bart
>
> -----Original Message-----
> From: Discussion of advanced .NET topics.
> [mailto:[EMAIL PROTECTED] On Behalf Of Tony Nassar
> Sent: zondag 25 februari 2007 4:26
> To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM
> Subject: Re: [ADVANCED-DOTNET] Virtual methods in .NET - was Implementing an
> Interface - C# vs. VB.NET
>
> Assuming your question isn't simply rhetorical, the reason is very simple:
> the CLS didn't make it its business to force *every* language to be like
> Java in this respect. Anders Hjellberg has explained exactly why C# is this
> way; check out the interviews with him at artima.com.
>
> > Anybody know why methods aren't virtual by default in .NET?
> > It seems like a really bad default to have all methods non-virtual.
>
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