Set class generic value in constructor only

Question

There is any way to set the generic type (T) of class in the constructor only, but not in the declaration?

public class Gen<T>
{
}

public class Da
{
}

public class Program
{
    public static Gen<?> gen;

    public static void Main(string[] args)
    {
        gen = new Gen<Da>();
    }
}

Answer 1

If I understand your requirements correctly, the easiest way to achieve this is to have a non-generic interface:

interface IGen { }

Then your generic class can be:

class Gen<T> : IGen { }

And the usage is:

IGen objectGen = new Gen<object>();
IGen intGent = new Gen<int>();