This question already has answers here:
Extension methods require declaring class to be static
(1 answer)
Why are extension methods only allowed in non-nested, non-generic static class?
(3 answers)
Closed 9 years ago.
I mean, I'm pretty sure it is a good habit anyway, but are there any technical/conceptual reasons why this is enforced by the compiler? Or is it enforcing aesthetics only?
There are no reasons for this behavior below the C# layer. Starting with the IL layer extension methods and static classes do not exist (except for either unimportant changes or custom attributes).
It is a choice the language designers made, supposedly for code clarity. It does not have to be this way for any fundamental reason.
There are other similar restrictions as well. For example you can't have extensions defined in nested classes.
For my understanding this is a conceptual move.
The static class acts like a pure container for methods and itself does not represents the object, and the extension method by itself is the method that only processes the input and does not acts like a part of the objects behavior.
That is why I think they are very similar by its nature in the C# and probably that is why they where linked together by the language.
Related
This question already has answers here:
In C#, what is the purpose of marking a class static?
(5 answers)
Closed 4 years ago.
While learning about static classes, I went through many forums as per my understanding I got to know that static class members can be accessed directly using class name and hence not required to create object of that class which in turn helps save memory and faster execution of program.
So my question is if this is the case then why not always use static class over normal class.
I know my question may be little weird, also I may be wrong with the concepts. Please if any one can explain this in detail with example. would be great help.
A static class can not be instantiated. E.g. you can't use new to create an object of that class in C#.
There are many situations where you might want to create multiple objects of a class.
This question already has answers here:
When do you use the "this" keyword? [closed]
(31 answers)
Closed 4 years ago.
I'm looking at code from another programmer and style differences aside, they do something I don't.
On every single reference to the class' own variables and methods, they precede it with this. (ie. this.Init() x Init() )
On my side, I've mostly used this to pass a reference to the instance to other classes, or, on occasion, when I needed to differentiate from base.
Is there any particular advantage in explicitly referring to this every time?
No functional difference. Perhaps the project coding style guidelines require it, in which case you should use it.
This question already has answers here:
Extension methods versus inheritance
(9 answers)
Closed 6 years ago.
I am facing this question regularly in interview. But I am not getting it's answer anywhere.Please help me.
Inheritance and extension methods are entirely orthogonal. It's just a simple way of writing a function in C# using the familiar . syntax. They only look similar if you use inheritance for code reuse, which tends to be frowned upon (but make sure you understand why - "best" practices are context-sensitive :)).
In any case, I'd expect the question is there to get you talking. Don't focus too hard on what the "right" answer is - just outline what inheritance is used for according to you, and what extension methods are used for, and what benefits and drawbacks each of those has. Get the dialog running.
For me, for example, extension methods are all about making common functions against an interface. That is, the functions add functionality on top of an interface (or class) while only using its public interface. This makes the "size" of the interface available to the function much smaller, which in turn makes it much easier to reason about.
Different people use extension methods differently, just like different people use inheritance differently. However, I find that as you shift from inheritance to composition, extension methods become more and more useful (and really, natural). Inheritance is a very specific technique that started being used for pretty much everything with little reason, but that's a big topic on Programmers.SE already anyway, just like the composition vs. inheritance debate :))
This question already has answers here:
When do you use extension methods, ext. methods vs. inheritance?
(7 answers)
Closed 9 years ago.
I have been using C# extension methods for a while now and I find them to be really handy. However I am not really sure of what is the most ideal situation to use them, I feel at times I abuse them. When would you recommend the use of extension methods ?
IMO when either it's really an extension (and not a core/critical operation), or when it's a shortcut.
An example of an extension:
Often in sandbox applications (but it could also be used in real ones, of course) is extending IEnumerable with a Print method.
The print method shouldn't be there (that is: it shouldn't be a part of the IEnumerable class), but it's helping and making the syntax easier and cleaner. Also, you probably wouldn't want to ship a library with it as a part of that class.
An example of a shortcut:
Another thing I find myself often creating is an helper extension for objects with containers. Instead of calling Items.Add and similar, I just make an AddItem extension-method.
Something to consider is that it's just syntactic sugar, that is, it's for the you - the developer. So for .NET types and such use it when you think it's a good idea and will make things cleaner.
When it comes to "Should this method be an extension or a member?" see the first sentence in this answer, and also look here & here for more information.
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Why seal a class?
I haven't seen a lot of classes with this modifier, however I'm wondering in which kind of scenarios this would be useful.
In case you do not wand anyone to extend a class.
Classic example is a String class, it's self-sufficient and implements flyweight pattern, that might be easily destroyed if anyone could overwrite it's methods/properties.
You want to use the sealed class if you provide your API that doesn't need to be changed, for any of above reasons.