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Answer 1

+17 A:

No they do not exist in C# 3.0 and will not be added in 4.0. It's on the list of feature wants for C# so it may be added at a future date.

At this point the best you can do is GetXXX style extension methods.

JaredPar 2009-03-06 14:33:40

Similarly with generic properties: you have to use 'GetXXX<>' syntax.

Jay Bazuzi 2009-03-06 15:39:13

ok, that's what I thought. @Jay, yeah, I hate that too, hehe. Especially the inability to have a generic indexer... *sigh*

Svish 2009-03-06 17:51:36

Link to list of feature wants?

Dan Esparza 2010-10-22 05:45:08

Answer 2

+10 A:

No, they don't exist.

I know that the C# team was considering them at one point (or at least Eric Lippert was) - along with extension constructors and operators (those may take a while to get your head round, but are cool...) However, I haven't seen any evidence that they'll be part of C# 4. As for C# 5 and onwards - I think it's too early to speculate.

Jon Skeet 2009-03-06 14:34:18

IMO they wont add anything of value. How would you handle the setter? The purpose of properties is to 'hide the field'.

leppie 2009-03-06 14:36:19

Yes, and they could still hide the field - setting a single property might set two properties underneath, or vice versa. (Imagine something with a normal Size property, and Width/Height extension properties, or vice versa.) They'd be more useful as read-only ones though, I suspect.

Jon Skeet 2009-03-06 14:46:07

You can't bind to extension methods... being able to add your own properties for databinding could be helpful in many situations.

Nick 2009-03-06 14:46:10

Nick, that's where you use TypeCpnverter and PropertyDescriptors :)

leppie 2009-03-06 14:48:28

@Jon: Hooray for double side-effects! :) I'd rather not.

leppie 2009-03-06 14:49:13

@leppie: I agree that most of the time that's not what you want. I wouldn't be surprised to find some useful situations though. And as I say, most of the time I'd want them as read-only properties.

Jon Skeet 2009-03-06 15:04:53

Answer 3

A:

Is () too much extra to type?

leppie 2009-03-06 14:34:51

This question is about extension properties, but you want to challenge the merit of properties in general? Pointless.

Jay Bazuzi 2009-03-06 15:01:50

yes they are. cause the () to me signify a method, which is an action, a verb.

Svish 2009-03-06 17:50:41

-1: If you don't have an answer, don't answer. If you use methods, you can't only add (). You have to implement two methods, a getter and a setter. The implementation takes some more effort, they don't match what you normally expect in C#, you need two different names for the methods, and the name must be a verb ("Get...", "Set...").

chiccodoro 2010-09-09 06:33:41

Answer 4

+1 A:

No they do not exist. As for why, I don't know...

See also this SO topic.

Razzie 2009-03-06 14:35:34

Answer 5

A:

@leppie: There are situations where extension methods just won't cut it. For instance, I wish I could define an extension property for the IgnoreAttribute type that comes with the Microsoft unit testing framework, so I can include a Reason property that gets set in the attribute. Right now, I'm using a comment to include this reason, but that is significantly more difficult to pull out of the code programmatically, than just querying a Reason property on the attribute object.

Of course, I can understand the extra difficulty of implementing this, from Microsoft's perspective... where, for instance, will the values of these extension properties be stored? :)

Kenneth LeFebvre 2010-08-05 18:47:44

@Kenneth: You're reply is supposed to be a "comment" on leppie's answer, not an individual answer. Just so you know...

chiccodoro 2010-09-09 06:36:13

Thanks.... I'm still getting familiar with Stack Overflow.

Kenneth LeFebvre 2010-09-09 17:25:33

Answer 6

A:

Not an answer to the question but might be interesting still:

Property extensions in C# 5.0

// A product type in this sample has a property Name of type String
var product = new Product();

// This will print "Product.Name.IsDirty: False"
Console.WriteLine("Product.Name.IsDurty: {0}", product.Name.IsDirty);

// Now let's try to update product's Name property
product.Name = "T-Short";

// And now this will print "Product.Name.IsDirty: True"
Console.WriteLine("Product.Name.IsDurty: {0}", product.Name.IsDirty);

// Then when you try to save this product in database, it will be easier
// for your Store Repository detect which fields must be saved
// and which can be skipped

storeRepository.Add(product);
storeRepository.SubmitChanges();

Koistya Navin 2010-09-09 02:37:05

While interesting, this question deals with the property equivalent of extension methods. The keywords here may match, but they are of an entirely different meaning!

Anthony Pegram 2010-09-09 02:43:03

The blog post referenced is complete supposition and represents a *possible* (although highly unlikely) implementation. Extension properties have been considered several times before and don't "make the cut" to be included in the language and probably won't for a good while since there are usually bigger features that have much larger impact.

Scott Dorman 2010-09-09 03:17:05

Answer 7

A:

This is why they don't exist.

Not enough time
Turned out to not really solve the problems they were thought to be solving

http://blogs.msdn.com/b/ericlippert/archive/2009/10/05/why-no-extension-properties.aspx

Simon_Weaver 2010-10-22 05:43:16

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