> <hufaun***@yahoo.com> wrote:
> > I have an interface where I would like to have some static functions.
> > When I add "static" to any of the interface functions I get the
> > following error: "The modifier 'static' is not valid for this item".
> > Why is it not possible to define static functions in an interface?
>
> The CLR allows static methods to be implemented in interfaces, but even
> then you couldn't just specify a static method which has to be
> implemented by the type implementing the interface. C# doesn't even let
> you put the static method in there in the first place.
>
> I agree it would be useful sometimes, but consider: how would you call
> the static method in the first place?
>
> --
> Jon Skeet - <sk***@pobox.com>
> http://www.pobox.com/~skeet   Blog: http://www.msmvps.com/jon.skeet
> If replying to the group, please do not mail me too

> Hi
>
> First of all we should understand the keyword static; static says that
> it would be having its own memory area irrespective of its instance
> means this function will be loaded into the memory without having its
> instance.
>
> Now think if we have an interface and have one static function declared
> in it without body. Now what will be loaded into the memory and if user
> will call IInterface.StaticFunction(), what will be executed. So I
> think its totally useless having a static function in interface.
>
>
> -Rohit
>
> Jon wrote:
> > <hufaun***@yahoo.com> wrote:
> > > I have an interface where I would like to have some static functions.
> > > When I add "static" to any of the interface functions I get the
> > > following error: "The modifier 'static' is not valid for this item".
> > > Why is it not possible to define static functions in an interface?
> >
> > The CLR allows static methods to be implemented in interfaces, but even
> > then you couldn't just specify a static method which has to be
> > implemented by the type implementing the interface. C# doesn't even let
> > you put the static method in there in the first place.
> >
> > I agree it would be useful sometimes, but consider: how would you call
> > the static method in the first place?
> >
> > --
> > Jon Skeet - <sk***@pobox.com>
> > http://www.pobox.com/~skeet   Blog: http://www.msmvps.com/jon.skeet
> > If replying to the group, please do not mail me too

> news:1157640328.484248.192830@b28g2000cwb.googlegroups.com...
> > An interface defines just a contract and not the implementation itself.
> > So if the static keyword would be allowed for a function then it would
> > only say that the class implementing the interface must declare this
> > function as static. Therefore, unless I missed something I think your
> > argument is not valid.
>
> The "interface as a contract" is a useful concept, but not 100% correct.
>
> Really, an interface is a restricted abstract class, with all functions
> being pure virtual and no data.  So the interface has a v-table layout which
> needs to be followed by implementing classes, just like an abstract class
> has a v-table layout used by subclasses.
>
> Now, just like the Region class has a static member function Union which
> operates on a group of Region objects, MSIL allows an interface to have
> static member functions and properties which are generally useful and
> applied to the entire tree of class types implementing that interface.
>
> For example, if an interface declared an instance Guid property, it would be
> useful to have a static method which returns the instance (of some derived
> type) given the Guid.  This static method is part of the interface type, and
> not a contractual constraint on implementors.
>
> The static keyword consistently means "part of the declaring type, not part
> of any object".  Thus you can see that an abstract static method is
> impossible.
>
> To get something like static methods on derived types, you can borrow from
> COM's playbook.  In COM implementations in C (not C++), you had to set up
> the object's v-table by declaring a structure of function pointers.  You can
> do the same, by having a class of delegate fields.  The interface declares a
> property with that class type.  Each implementing class needs to initialize
> one copy of this class in the type initializer, to point to its set of
> static methods, and then the (instance) property just returns the static
> field which refers to the delegate group.
>
> Something like:
>
> class RequiredStaticMethods
> {
>     public readonly EventHandler a;
>     public readonly EventHandler b;
>     public RequiredStaticMethods(EventHandler a, EventHandler b)
>     {
>         if (a == null || b == null) throw new ArgumentNullException();
>         this.a = a;
>         this.b = b;
>     }
> }
>
> interface INeedStaticMethods
> {
>     RequiredStaticMethods StaticMethods { get; }
> }
>
> class AnImplementation : INeedStaticMethods
> {
>     private static void OnA(object sender, EventArgs e) {}
>     private static void OnB(object sender, EventArgs e) {}
>     public static readonly RequiredStaticMethods StaticMethods = new
> RequiredStaticMethods(OnA, OnB);
>     RequiredStaticMethods INeedStaticMethods.StaticMethods { get { return
> StaticMethods; } }
> }
>
> now you can call:
> AnImplementation.StaticMethods.a(...);
> INeedStaticMethods x = new AnImplementation(); // call static method of
> fixed type
> x.StaticMethods.b(...); // dynamic dispatch to static method based on
> runtime type of x

>
> Thanks
>

> news:1157608659.592263.96770@b28g2000cwb.googlegroups.com...
> >I have an interface where I would like to have some static functions.
> > When I add "static" to any of the interface functions I get the
> > following error: "The modifier 'static' is not valid for this item".
> > Why is it not possible to define static functions in an interface?
>
> Maybe you should make an abstract class instead?
>
> >
> > Thanks
> >

> >I have an interface where I would like to have some static functions.
> > When I add "static" to any of the interface functions I get the
> > following error: "The modifier 'static' is not valid for this item".
> > Why is it not possible to define static functions in an interface?
>
> I just whining abou this the other day in a blog entry. It's a feature I
> would quite like to see, as well as some other realated stuff.
>
> http://www.coversant.net/dotnetnuke/Default.aspx?tabid=88&EntryID=14
>
> Unfortunatly, all I have is questions and suggestions - no good solutions.
>
> --
> Chris Mullins