private MainClass()
    {
        myType = new MyType();
    }

    public MainClass(string inParm)
        : base()
    {
        myParm = inParm;
    }
}

public class MainClass
{
    private MyType myType = null;
    private string myParm = string.Empty;

    private MainClass()
    {
    }

    public MainClass(string inParm)
        : base()
    {
        myType = new MyType();
        myParm = inParm;
    }
}