Restrict class instantiation

Question

In C#, is there a way to stop instantiating class, say after 'n' instantiations ? This link doesn't help much.

About trying out things, I was thinking of making the class static, but 'n' instantiations have to achieved before stopping the instantiations. Is it possible through Reflection ?

Answer 1

You may have a private static counter, increment it in the constructor and throw an Exception if your limit is reached. But notice, this is a very strange and most probably bad design. A better way would be a factory pattern

class LimitedInstantiation
    {
        private static int instCounter = 0;
        public LimitedInstantiation()
        {
            instCounter++;
            // limit your number of instances 
            if (instCounter > 3)
            {
                throw new Exception("Limit of instances reached");
            }
        }

        ~LimitedInstantiation()
        {   
            // Reduce your number of instances in the destructor
            instCounter--;
        }
    }

You can test if like this:

try
{
    var instance1 = new LimitedInstantiation();
    var instance2 = new LimitedInstantiation();
    var instance3 = new LimitedInstantiation();
    // this should fail.
    var instance4 = new LimitedInstantiation();
}
catch (Exception e)
{
    Console.WriteLine(e);
}