CSharp/C#, new Singleton() ( Can I override the new operator to return a singleton?)

Olav.N
#1 / 9

new Singleton() ( Can I override the new operator to return a singleton?)

Is there some way to have the new-operator
return a Singleton?

I.e. that
new Singleton()
always return a reference to the same object?

The reason I need this is that I want to share
a DataSet between forms, the dataset must be
available at design time, and the Windows
Forms Designer seems to want a new-operator.

Thanks!
Olav

Wed, 04 Aug 2004 02:41:45 GMT

Armin Zingle
#2 / 9

new Singleton() ( Can I override the new operator to return a singleton?)

Quote:

> Is there some way to have the new-operator
> return a Singleton?

> I.e. that
> new Singleton()
> always return a reference to the same object?

> The reason I need this is that I want to share
> a DataSet between forms, the dataset must be
> available at design time, and the Windows
> Forms Designer seems to want a new-operator.

untested VB syntax:

Private Shared _Singleton as New MyClass

private Sub New
'empty. private declaration avoids external creation
end sub

Public Shared Readonly Property Singleton As MyClass
Get
Return _Singleton
End Get
end sub

Accessing MyClass.Singleton always returns the same object.

Armin

Wed, 04 Aug 2004 05:28:50 GMT

G. Asho
#3 / 9

new Singleton() ( Can I override the new operator to return a singleton?)

Declare the constructor as Shared.
Shared Sub New()
'...
End Sub

...Ashok

Quote:

> Is there some way to have the new-operator
> return a Singleton?

> I.e. that
> new Singleton()
> always return a reference to the same object?

> The reason I need this is that I want to share
> a DataSet between forms, the dataset must be
> available at design time, and the Windows
> Forms Designer seems to want a new-operator.

> Thanks!
> Olav

Wed, 04 Aug 2004 11:10:42 GMT

Olav.N
#4 / 9

new Singleton() ( Can I override the new operator to return a singleton?)

I dont know VB/VB.NET, but I think this is "just"
a standard Singleton-pattern (It might have solved
my problems if I were using VB though).

Olav

Quote:

> untested VB syntax:

> Private Shared _Singleton as New MyClass

> private Sub New
> 'empty. private declaration avoids external creation
> end sub

> Public Shared Readonly Property Singleton As MyClass
> Get
> Return _Singleton
> End Get
> end sub

> Accessing MyClass.Singleton always returns the same object.

> Armin

Wed, 04 Aug 2004 19:26:21 GMT

Olav.N
#5 / 9

new Singleton() ( Can I override the new operator to return a singleton?)

Quote:

> Declare the constructor as Shared.
> Shared Sub New()
> '...
> End Sub

> ...Ashok

Perhaps in VB.NET, but in C# it doesn't change anything
(The default non-static constructor is still there and is
called)

Olav

Quote:

> > Is there some way to have the new-operator
> > return a Singleton?

Wed, 04 Aug 2004 20:37:10 GMT

Bela Isto
#6 / 9

new Singleton() ( Can I override the new operator to return a singleton?)

Try this:
public class foo
{
private static foo retFoo;
private foo() {}
public static foo Instance()
{
if(retFoo == null)
retFoo = new foo();
return retFoo;
}

Quote:

}

Quote:

> > Declare the constructor as Shared.
> > Shared Sub New()
> > '...
> > End Sub

> > ...Ashok
> Perhaps in VB.NET, but in C# it doesn't change anything
> (The default non-static constructor is still there and is
> called)

> Olav

> > > Is there some way to have the new-operator
> > > return a Singleton?

Thu, 05 Aug 2004 02:12:49 GMT

Olav.N
#7 / 9

new Singleton() ( Can I override the new operator to return a singleton?)

I know the Singleton-pattern (Both with and without
a static constructor). My problem is an implemenation
that works with the new-operator.

Besides

Quote:

>private static foo retFoo;

Should be (I think)
private static foo retFoo = null;

Olav

************************************************************

Quote:

> Try this:
> public class foo
> {
> private static foo retFoo;
> private foo() {}
> public static foo Instance()
> {
> if(retFoo == null)
> retFoo = new foo();
> return retFoo;
> }
> }

> > > Declare the constructor as Shared.
> > > Shared Sub New()
> > > '...
> > > End Sub

> > > ...Ashok
> > Perhaps in VB.NET, but in C# it doesn't change anything
> > (The default non-static constructor is still there and is
> > called)

> > Olav

> > > > Is there some way to have the new-operator
> > > > return a Singleton?

Thu, 05 Aug 2004 19:38:34 GMT

M. Veurma
#8 / 9

new Singleton() ( Can I override the new operator to return a singleton?)

How about:

public class foo
{
private static foo retFoo = null;
private foo() {}
public static foo Instance()
{
if(retFoo == null)
retFoo = new foo();
return retFoo;
}

public void func()
{
....
}

Quote:

}

public class fooBar
{
private foo foo_instance;

public fooBar()
{
foo_instance = foo.Instance();
}

public void func()
{
foo_instance.func();
}

Quote:

}

Quote:

> I know the Singleton-pattern (Both with and without
> a static constructor). My problem is an implemenation
> that works with the new-operator.

> Besides
> >private static foo retFoo;
> Should be (I think)
> private static foo retFoo = null;

> Olav

> ************************************************************

Quote:

> > Try this:
> > public class foo
> > {
> > private static foo retFoo;
> > private foo() {}
> > public static foo Instance()
> > {
> > if(retFoo == null)
> > retFoo = new foo();
> > return retFoo;
> > }
> > }

> > > > Declare the constructor as Shared.
> > > > Shared Sub New()
> > > > '...
> > > > End Sub

> > > > ...Ashok
> > > Perhaps in VB.NET, but in C# it doesn't change anything
> > > (The default non-static constructor is still there and is
> > > called)

> > > Olav

> > > > > Is there some way to have the new-operator
> > > > > return a Singleton?

Fri, 06 Aug 2004 22:48:34 GMT

Mark Smit
#9 / 9

new Singleton() ( Can I override the new operator to return a singleton?)

Quote:

>Try this:
>public class foo
>{
> private static foo retFoo;
> private foo() {}
> public static foo Instance()
> {
> if(retFoo == null)
> retFoo = new foo();
> return retFoo;
> }
>}

You can use a static constructor to get rid of the test for null:

class Singleton
{
static Singleton instance;
static Singleton() { instance = new Singleton(); }
static public Singleton Instance() { return instance; }
private Singleton() {}
}

The static constructor is guaranteed to be called first.

--

Fri, 06 Aug 2004 23:46:19 GMT