Prevent usage of default constructor

Question

Is there a way to prevent the usage of the default constructor?

All I can think of is throwing an exception, but I would like something that causes a compile time er

Answer 1

You can just make it private:

private MyClass()
{
}

Alternatively (if you didn't know already) if you just declare a constructor with parameters, the default one isn't added by the compiler, e.g.

private MyClass(string myParameter)
{
    //Can't call new MyClass() anymore
}

Answer 2

Make it private.

So,

class SomeClass
{
    private SomeClass()
    {
    }

    public SomeClass(int SomeParam)
    {
    }
}

Answer 3

Aside from other answers, you can read following text, for more info on Singleton pattern, and some examples. Singleton pattern relies on constructor being private.

http://www.yoda.arachsys.com/csharp/singleton.html

Answer 4

• If everything in the class is static, consider making it a static class. That way, you won't get a constructor at all.
• If you want a parameterless constructor but you don't want it to be public, declare it explicitly and make it private (or internal etc)
• If you don't want a parameterless constructor but do want constructors with parameters, then just declare the parameterized constructor - the default constructor won't be generated for you

I think that should cover all bases...

Answer 5

One thing to mention that others have not. The default constructor should still be able to set up the default implementation bits, to avoid reuse. This is not a problem if it is private, as you can still chain down to a private constructor. You just make it unavailable to outside sources.

private MyClass()
{
}

public MyClass(string something) : this()
{
}

That solves the problem. Note, however, that protected may actually be a preferred implementation if the class is not sealed.