Static Methods

[Jim Heavey]

Hello, hoping you can clear up a little bit of confusion that I have on
creating/using static methods.

I want to create a class which hold all my "Utility Methods" for windows
forms. So I created a new project and added that project to my existing
project. The project "type" I selected was a "Class Library". What
this a correct choice.

So if I want to create "Static" methods, does the class itself have to
be static? There is no real reason to instatiate the class, so I am
guessing that I should make the class static. When I attempt to do
this, it tells me the modifier is not valid for this item. Have I got
the wrong format, or the wrong idea? Here is my code...

namespace WindowFormsUtil ities
{
/// <summary>
/// Summary description for Class1.
/// </summary>
public static class WindFormUtiliti es
{
public static WindFormUtiliti es()
{
//
// TODO: Add constructor logic here
//
}
public static bool SetComboBoxSele ctionError(Comb oBox cbo,
ErrorProvider err)
{
}

private bool[] SetComboBoxSele ctionError (ComboBox[] cbo,
ErrorProvider err)
{
}

}
}

[Sean Dudley]

Just make a regular class and make the methods (only) static. All data used
int her methods will also have to be declared static.
"Jim Heavey" <Ji*******@nosp am.com> wrote in message
news:Xn******** *************** **********@207. 46.248.16...

Hello, hoping you can clear up a little bit of confusion that I have on
creating/using static methods.

I want to create a class which hold all my "Utility Methods" for windows
forms. So I created a new project and added that project to my existing
project. The project "type" I selected was a "Class Library". What
this a correct choice.

So if I want to create "Static" methods, does the class itself have to
be static? There is no real reason to instatiate the class, so I am
guessing that I should make the class static. When I attempt to do
this, it tells me the modifier is not valid for this item. Have I got
the wrong format, or the wrong idea? Here is my code...

namespace WindowFormsUtil ities
{
/// <summary>
/// Summary description for Class1.
/// </summary>
public static class WindFormUtiliti es
{
public static WindFormUtiliti es()
{
//
// TODO: Add constructor logic here
//
}
public static bool SetComboBoxSele ctionError(Comb oBox cbo,
ErrorProvider err)
{
}

private bool[] SetComboBoxSele ctionError (ComboBox[] cbo,
ErrorProvider err)
{
}

}
}

[Mike Bird]

A class Library project is the correct project type, and no, you can't
create a static class. The general rule if you are creating a class that
has all static methods is to make it sealed, since deriving from the class
wouldn't gain anything, and to declare a private default constructor so no
one can create an instance of you class.
"Jim Heavey" <Ji*******@nosp am.com> wrote in message
news:Xn******** *************** **********@207. 46.248.16...

Hello, hoping you can clear up a little bit of confusion that I have on
creating/using static methods.

I want to create a class which hold all my "Utility Methods" for windows
forms. So I created a new project and added that project to my existing
project. The project "type" I selected was a "Class Library". What
this a correct choice.

So if I want to create "Static" methods, does the class itself have to
be static? There is no real reason to instatiate the class, so I am
guessing that I should make the class static. When I attempt to do
this, it tells me the modifier is not valid for this item. Have I got
the wrong format, or the wrong idea? Here is my code...

namespace WindowFormsUtil ities
{
/// <summary>
/// Summary description for Class1.
/// </summary>
public static class WindFormUtiliti es
{
public static WindFormUtiliti es()
{
//
// TODO: Add constructor logic here
//
}
public static bool SetComboBoxSele ctionError(Comb oBox cbo,
ErrorProvider err)
{
}

private bool[] SetComboBoxSele ctionError (ComboBox[] cbo,
ErrorProvider err)
{
}

}
}

[Mattias Sjögren]

Jim,

So if I want to create "Static" methods, does the class itself have to
be static? There is no real reason to instatiate the class, so I am
guessing that I should make the class static. When I attempt to do
this, it tells me the modifier is not valid for this item. Have I got
the wrong format, or the wrong idea? Here is my code...

Unless you're using the Whidbey version of C#, there's no such thing
as a static class. You can make it abstract or add a private
constructor to prevent it from being instantiated.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[n!]

> So if I want to create "Static" methods, does the class itself have to

be static? There is no real reason to instatiate the class, so I am
guessing that I should make the class static. When I attempt to do
this, it tells me the modifier is not valid for this item. Have I got
the wrong format, or the wrong idea? Here is my code...

I generally make classes with only static members, sealed with a private
constructor. Similar to:

public sealed class MyUtilityClass
{
private MyUtilityClass( ) // Prevent direct instantiation.
{
}
}

The 'sealed' property prevents someone from inheriting the class, the
private constructor prevents someone from creating an instance of the class
:) From reading your mail I think 'sealed' is basically the equivalent of
what you were expecting a 'static' class to be.

n!

[Jon Skeet [C# MVP]]

n! <nf********@nom ailplease.com> wrote:

I generally make classes with only static members, sealed with a private
constructor. Similar to:

public sealed class MyUtilityClass
{
private MyUtilityClass( ) // Prevent direct instantiation.
{
}
}

The 'sealed' property prevents someone from inheriting the class, the
private constructor prevents someone from creating an instance of the class
:) From reading your mail I think 'sealed' is basically the equivalent of
what you were expecting a 'static' class to be.

There's no real need to make the class sealed as well as only having a
private constructor - just the fact that its only constructor is
private means that you can't inherit from it.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

Then why does the compiler permit this combination? Isnt this like havint a
string as a const and static? You cant because it makes no sense, just as
what you say , it makes no sense.
"Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@msnews.micros oft.com...

n! <nf********@nom ailplease.com> wrote:

I generally make classes with only static members, sealed with a private
constructor. Similar to:

public sealed class MyUtilityClass
{
private MyUtilityClass( ) // Prevent direct instantiation.
{
}
}

The 'sealed' property prevents someone from inheriting the class, the
private constructor prevents someone from creating an instance of the class :) From reading your mail I think 'sealed' is basically the equivalent of what you were expecting a 'static' class to be.

There's no real need to make the class sealed as well as only having a
private constructor - just the fact that its only constructor is
private means that you can't inherit from it.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

<di********@dis cussion.microso ft.com> wrote:

Then why does the compiler permit this combination? Isnt this like havint a
string as a const and static? You cant because it makes no sense, just as
what you say , it makes no sense.

I think there's a difference in the level of logical connection there.
It's not that there's anything *syntactically* redundant about there
being a sealed class with only a private constructor, it's only
*semantically* redundant.

It would be reasonable of the compiler to complain, but I don't think
it's particularly necessary for it to do so.

(There's also the fact that the two will end up in different IL - a
class with only private constructors is *effectively* sealed, it isn't
*actually* sealed.)

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[n!]

> There's no real need to make the class sealed as well as only having a

private constructor - just the fact that its only constructor is
private means that you can't inherit from it.

That's true, though the private constructor is there to prevent creation of
a class instance rather than prevent inheritance (even though it effectively
does that job as well), and the compile error is more meaningful when trying
to inherit a sealed class rather than a class with private constructors. :)

n!