Do we have extention properties in C# 3.0?

[Max2006]

Hi,

C# 3.0 extension methods become useful for us. Do we have the similar
concept for extension properties?

Thank you,
Max

[Peter Duniho]

On Wed, 23 Jul 2008 15:42:19 -0700, Max2006 <al*******@news group.nospam>
wrote:

C# 3.0 extension methods become useful for us. Do we have the similar
concept for extension properties?

No, I don't think so. But interesting idea. Maybe they're thinking about
it.

[=?ISO-8859-1?Q?Arne_Vajh=F8j?=]

Max2006 wrote:

C# 3.0 extension methods become useful for us. Do we have the similar
concept for extension properties?

No.

And there is a syntax problem.

Properties are distinguished from methods by the fact that they
do not have an argument list.

The object being extended is passed as an extra argument.

How should the syntax be to distinguish between
a method with no arguments and a property ?

Arne

[Peter Duniho]

On Wed, 23 Jul 2008 17:11:48 -0700, Arne Vajhøj <ar**@vajhoej.d kwrote:

[...]
How should the syntax be to distinguish between
a method with no arguments and a property ?

Syntax for an extension property:

public int MyProperty(this SomeClass arg0)
{
get;
set;
}

Just because properties as declared now don't include an argument list,
that doesn't mean they couldn't. There's enough other information in the
declaration block to distinguish a property from a method, I believe.

No doubt there are other valid ways to allow the declaration of an
extension property, but the above seems most straightforward and
consistent to me.

Pete

[=?UTF-8?B?QXJuZSBWYWpow7hq?=]

Peter Duniho wrote:

On Wed, 23 Jul 2008 17:11:48 -0700, Arne Vajhøj <ar**@vajhoej.d kwrote:

>How should the syntax be to distinguish between
a method with no arguments and a property ?

Syntax for an extension property:

public int MyProperty(this SomeClass arg0)
{
get;
set;
}

Just because properties as declared now don't include an argument list,
that doesn't mean they couldn't. There's enough other information in
the declaration block to distinguish a property from a method, I believe.

No doubt there are other valid ways to allow the declaration of an
extension property, but the above seems most straightforward and
consistent to me.

It will require readers to check the body to see if something is
a method or a property.

Not very nice syntax.

Arne

[Peter Duniho]

On Wed, 23 Jul 2008 17:59:45 -0700, Arne Vajhøj <ar**@vajhoej.d kwrote:

It will require readers to check the body to see if something is
a method or a property.

Not very nice syntax.

I don't personally see the big deal. But if you don't like that, how
about this:

public int MyProperty
{
this SomeClass arg0;
get;
set;
}

Or provide your own suggestion. Complaining that it can't be done because
of a syntax problem is dumb. That's what we pay the language designers
the big bucks for. Let them figure it out and come up with something that
is reasonably elegant and makes life easy for the compiler writer, if
that's so important.

Pete

[Jon Skeet [C# MVP]]

On Jul 24, 12:22*am, "Peter Duniho" <NpOeStPe...@nn owslpianmk.com>
wrote:

C# 3.0 extension methods become useful for us. Do we have the similar *
concept for extension properties?

No, I don't think so. *But interesting idea. *Maybe they're thinking about *
it.

It's definitely been considered. I don't know whether it's actually
going to be in C# 4 or not. (I'm looking forward to a first proper
peek at C# 4, whenever that happens. I expect it to be a much smaller
set of changes than either 2 or 3 though.)

Jon

[Frans Bouma [C# MVP]]

Jon Skeet [C# MVP] wrote:

On Jul 24, 12:22 am, "Peter Duniho" <NpOeStPe...@nn owslpianmk.com>
wrote:

>>C# 3.0 extension methods become useful for us. Do we have the similar
concept for extension properties?

No, I don't think so. But interesting idea. Maybe they're thinking about
it.

It's definitely been considered. I don't know whether it's actually
going to be in C# 4 or not. (I'm looking forward to a first proper
peek at C# 4, whenever that happens. I expect it to be a much smaller
set of changes than either 2 or 3 though.)

I think the C# team, IF they implement extension properties, should
take that famous step back and look again at what the REAL reason is
people want extension properties (as they represent state): AOP. So they
should use their influence to turn the CLR team over to implement AOP at
the CLR level once and for all.

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#)
------------------------------------------------------------------------

[Frans Bouma [C# MVP]]

Peter Duniho wrote:

On Wed, 23 Jul 2008 17:59:45 -0700, Arne Vajhøj <ar**@vajhoej.d kwrote:

>It will require readers to check the body to see if something is
a method or a property.

Not very nice syntax.

I don't personally see the big deal. But if you don't like that, how
about this:

public int MyProperty
{
this SomeClass arg0;
get;
set;
}

Or provide your own suggestion. Complaining that it can't be done
because of a syntax problem is dumb. That's what we pay the language
designers the big bucks for. Let them figure it out and come up with
something that is reasonably elegant and makes life easy for the
compiler writer, if that's so important.

Heh :)

I think this syntax is parsable, the other is very hard to do, as it
requires a looooooong look ahead.

Nevertheless, there's a practical problem as well: Extension methods
are static, i.e. don't have state, they work on the object passed in.
However, a property represents state, on the object they're a part of.
An extension property therefore should be static, but ... what should
that 'set' do? set a property on arg0? Then why not set the property
directly instead of calling this extension property?

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#)
------------------------------------------------------------------------

[Jon Skeet [C# MVP]]

On Jul 24, 8:53*am, "Frans Bouma [C# MVP]"
<perseus.usenet NOS...@xs4all.n lwrote:

It's definitely been considered. I don't know whether it's actually
going to be in C# 4 or not. (I'm looking forward to a first proper
peek at C# 4, whenever that happens. I expect it to be a much smaller
set of changes than either 2 or 3 though.)

* * * * I think the C# team, IF they implement extension properties, should
take that famous step back and look again at what the REAL reason is
people want extension properties (as they represent state): AOP. So they
should use their influence to turn the CLR team over to implement AOP at
the CLR level once and for all.

I don't immediately see the AOP connection, but I'm sure you're right
- could you elaborate?

I see extension properties as a way of providing different views on
existing state.

Jon