Question

How can i create a class with zero constructor, just like MessageBox class which has no constructor.
I can not make this class static, beacause a public static method is declared in it, and that method makes object of this class.
in C# 3.5

i want to make this class just like System.Windows.Forms.MessageBox class,
in which there is no constructor and
when we create object of this class error occurres :

this class has no constructor

where as a class with a private constructor when object creates error occurrs –

the constructor is not accessible due to its protection level.

Answer 1

The only way to create a class without a constructor is to use static class.

However, it seem you want to be able to create instances of this class from inside the class itself, which is not possible with a static class. For that, you should give the class a private constructor:

class Foo
{
    private Foo() { }

    public static Foo Create()
    {
        return new Foo(); // Only members of Foo can directly invoke the constructor.
    }
}

If a method outside of Foo in the same assembly tries to instantiate Foo, the message given will be that the constructor is not accessible due to its protection level. If you try to access it from another assembly, it will give the message that Foo has no constructors.