Create instance of the class from base class

Question

I have DataAccess class which is derived from DataAccessor. DataAccessor class is the DB base class which I use in all all projects.

Instance method is the helper to create new instance of the DataAccess class. I would like to move Instance method to DataAccessor base class and create new insatnces of derived classes from base class. How to do that?

public class DataAccess : DataAccessor
{

    public static DataAccess Instance
    {
        get
        {
            return new DataAccess();
        }
    }
}

public abstract class DataAccessor 
{
}

Moo-Juice · Accepted Answer · 2011-07-28 12:42:07Z

3

public class Base<T> where T : new()
{
    public static T Instance
    {
        get { return new T(); }
    }
}

public class Derived : Base<Derived>
{
}

answered Jul 28, 2011 at 12:42

Moo-Juice

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6 Comments

iandotkelly Over a year ago

Interesting. Can you point me at an example somewhere of something like this being used?

Yiğit Yener Over a year ago

I can use this class to create integers. int foo = Base<int>.Instance; What about that?

Moo-Juice Over a year ago

@iandotkelly, personally the only thing I can think of, off the bat, is a generic singleton implementation. But we all know how bad they are :)

Evren Kuzucuoglu Over a year ago

@Moo-Juice: this is not Singleton, this is Factory. Singleton is when you can only call new once.

Moo-Juice Over a year ago

@GFK, I am aware of that. iandotkelly asked why you might use something like this, obviously in the singleton case there would be a private static member and a check.

|

iandotkelly · Accepted Answer · 2011-07-28 12:43:54Z

3

Have you considered the Abstract Factory Pattern?

answered Jul 28, 2011 at 12:43

iandotkelly

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