Several rules about C# come into play here:
-
Each class must have a constructor (In order to be, well constructed)
-
If you do not provide a constructor, a constructor will be provided for you, free of change, automatically by the compiler.
This means that the class
class Demo{}
upon compilation is provided with an empty constructor, becoming
class Demo{ public Demo(){} }
and I can do
Demo instance = new Demo();
-
If you do provide a constructor (any constructor with any signature), the empty constructor will not be generated
class Demo{ public Demo(int parameter){} } Demo instance = new Demo(); //this code now fails Demo instance = new Demo(3); //this code now succeeds
This can seem a bit counter-intuitive, because adding code seems to break existing unrelated code, but it’s a design decision of the C# team, and we have to live with it.
-
When you call a constructor of a derived class, if you do not specify a base class constructor to be called, the compiler calls the empty base class constructor, so
class Derived:Base { public Derived(){} }
becomes
class Derived:Base { public Derived() : base() {} }
So, in order to construct your derived class, you must have a parameterless constructor on the base class. Seeing how you added a constructor to the Products, and the compiler did not generate the default constructor, you need to explicitly add it in your code, like:
public Products()
{
}
or explicitly call it from the derived constructor
public FoodProduct()
: base(string.Empty, string.Empty, 0, 0, 0, 0)
{
}