When is it appropriate to use static methods?

[Tom]

This is not intuitivelly clear.

[Ben Dewey]

Tom,

Static methods are methods that do not share any variables. the are the
same as VB6 sub routines that our outside of a class.

Example:
class Foo
{
private string thisTest = "test";
public string MyString()
{
return thisTest;
}

public static MyStaticString( )
{
return "test";
}
}

usage:

when using a static method you can just call
string test = Foo.MyStaticStr ing();

if it is not static you have to create and instance of the class

Foo myFoo = new Foo();
string test = myFoo.MyString( );

Basically is all boils down to memory usage. a static method is shared,
where as a non-static method gets created for every instance of the class.
Hope this makes sense?
"Tom" <nf*@nospam.com > wrote in message
news:%2******** ********@TK2MSF TNGP10.phx.gbl. ..

This is not intuitivelly clear.

[Kristofer Gafvert]

Use a static method when the method does not belong to a specific object.

For example, if you look at the Math class in .NET framework, you will see
that all methods are static. Why? Because there is no reason to must create
an object to use the methods. Why would you want to create an object of the
Math class, when all you want is the absolute value of something? No, there
is no reason to do this, and therefore, the method is static.

So when you design a class, ask yourself:

Does this method belong to an object, or the class itself?

A method belongs to an object, if it modifies the state of the object. If
the method does not modify a specific object, it can most likely be static.

Another example, suppose that you want to know how many objects of a class
that is created (don't ask me why...). For this task, you could create a
static method GetNumberOfObje cts() (and you obviously need a static field,
and some code in the constructor too). Why would i have it static, you might
ask. Well, answer the above question, and you will see. The method does not
belong to any specific object. Additionally, it does not modify any object.

I hope this makes sense.

--
Regards,
Kristofer Gafvert - IIS MVP
http://www.ilopia.com - When you need help!
"Tom" <nf*@nospam.com > wrote in message
news:%2******** ********@TK2MSF TNGP10.phx.gbl. ..

This is not intuitivelly clear.

[Tom]

"Kristofer Gafvert" <kg******@NEWSi lopia.com> wrote in message
news:u%******** ********@TK2MSF TNGP09.phx.gbl. ..

Use a static method when the method does not belong to a specific object.

What if the class is a singleton?

For instance, I have a WinForm application that does not allow multiple
instances of the application to run on the same workstation. This
application uses a Business Object singleton that caches global variables,
such as a reference to a DataSet that can be used by multiple MDI child
forms.

It doesn't seem particularly useful or efficient to create a new instance
every time I want to use one of the methods in this singleton.

[Kristofer Gafvert]

I would say that the same "rules" apply, no matter if it is a singleton or
not.

But, remember that a static method is not a substitute for not having a
proper class design. Is the method(s) we are talking about really relevant
for the class? Does they belong to the class, or to another (not yet
created?) class?

--
Regards,
Kristofer Gafvert - IIS MVP
http://www.ilopia.com - When you need help!
"Tom" <nf*@nospam.com > wrote in message
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"Kristofer Gafvert" <kg******@NEWSi lopia.com> wrote in message
news:u%******** ********@TK2MSF TNGP09.phx.gbl. ..

Use a static method when the method does not belong to a specific

object.
What if the class is a singleton?

For instance, I have a WinForm application that does not allow multiple
instances of the application to run on the same workstation. This
application uses a Business Object singleton that caches global variables,
such as a reference to a DataSet that can be used by multiple MDI child
forms.

It doesn't seem particularly useful or efficient to create a new instance
every time I want to use one of the methods in this singleton.

[AlexS]

IMO, statics are simplified equivalents of singletons. They grow from
globals - functions or variables. There is not much more.
I would suggest statics
- when you need global method, property or function
- when you need global variable
- when you need singleton, which exists during whole application lifetime

I found it easier to code singletons using statics. Excellent examples -
such classes like SystemInformati on or Environment.

HTH
Alex

"Tom" <nf*@nospam.com > wrote in message
news:%2******** ********@TK2MSF TNGP10.phx.gbl. ..

This is not intuitivelly clear.

[John Vottero]

"Ben Dewey" <be*******@scie ntiae.com> wrote in message
news:eW******** ******@tk2msftn gp13.phx.gbl...

[snip]

Basically is all boils down to memory usage. a static method is shared,
where as a non-static method gets created for every instance of the class.
Hope this makes sense?

This is not correct. The code is always shared whether it's static or not.
You're thinking of data, there's only one instance of static data,
non-static data is created for every instance.

John Vottero

[Ben Dewey]

My fault, that is what I was trying to get at.

Thanks for clearing that up.

"John Vottero" <Jo**@mvpsi.com > wrote in message
news:Os******** ******@TK2MSFTN GP10.phx.gbl...

"Ben Dewey" <be*******@scie ntiae.com> wrote in message
news:eW******** ******@tk2msftn gp13.phx.gbl...

[snip]

Basically is all boils down to memory usage. a static method is shared,
where as a non-static method gets created for every instance of the class. Hope this makes sense?

This is not correct. The code is always shared whether it's static or

not. You're thinking of data, there's only one instance of static data,
non-static data is created for every instance.

John Vottero

[Tom]

Should I make all the methods in a singleton static?

"AlexS" <sa***********@ SPAMsympaticoPL EASE.ca> wrote in message
news:es******** ******@TK2MSFTN GP11.phx.gbl...

IMO, statics are simplified equivalents of singletons. They grow from
globals - functions or variables. There is not much more.
I would suggest statics
- when you need global method, property or function
- when you need global variable
- when you need singleton, which exists during whole application lifetime

I found it easier to code singletons using statics. Excellent examples -
such classes like SystemInformati on or Environment.

HTH
Alex

"Tom" <nf*@nospam.com > wrote in message
news:%2******** ********@TK2MSF TNGP10.phx.gbl. ..

This is not intuitivelly clear.

[AlexS]

Singleton idea was to create a pattern, which allows you to have only one
instance of specific object during application lifetime. Static is object
(function) independent of any objects which might exist or not during
application lifetime. Statics exist and function always. So, there is some
difference - however, not very important for me. People fought with issues
with globals and invented singletons.

As about your question - general answer for general question - it depends.
If your singleton is providing global functionality - why not? If you want
some methods to be unavailable when singleton doesn't exist - might happen -
then no.

HTH
Alex

"Tom" <nf*@nospam.com > wrote in message
news:eE******** ******@tk2msftn gp13.phx.gbl...

Should I make all the methods in a singleton static?

"AlexS" <sa***********@ SPAMsympaticoPL EASE.ca> wrote in message
news:es******** ******@TK2MSFTN GP11.phx.gbl...

IMO, statics are simplified equivalents of singletons. They grow from
globals - functions or variables. There is not much more.
I would suggest statics
- when you need global method, property or function
- when you need global variable
- when you need singleton, which exists during whole application lifetime
I found it easier to code singletons using statics. Excellent examples -
such classes like SystemInformati on or Environment.

HTH
Alex

"Tom" <nf*@nospam.com > wrote in message
news:%2******** ********@TK2MSF TNGP10.phx.gbl. ..

This is not intuitivelly clear.