Question

I recently asked this question: Compiler error referencing custom C# extension method

Marc Gravell answer was perfect and it solved my problem. But it gave me something to think about…

If and Extension method must be placed on a Static Class and the method itself must be static, why can’t we create a static Extension method?

I understand that the parameter marked as ‘this’ will be used to allow access to an instance of the object we are extending. What I do not understand is why can’t a method be created to be static… it just seems to me that this is a senseless limitation…

My question is: Why can’t we create an extension method that will work as a static Method?

Answer 1

I expect the real answer is simply: there wasn’t a good use-case. For instances, the advantage is that it enables a fluent-API over existing types (that don’t themselves provide the logic) – i.e.

var foo = data.Where(x=>x.IsActive).OrderBy(x=>x.Price).First(); 

which enables LINQ:

var foo = (from x in data            where x.IsActive            order by x.Price            select x).First(); 

With static methods, this simply isn’t an issue, so there is no justification; just use the static method on the second type.

As it is, extension methods are not properly object orientated – they are a pragmatic abuse to make life easier at the expense of purity. There was no reason to dilute static methods in the same way.