Does not contain a constructor that takes 0 arguments
Solution 1:
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)
{
}
Solution 2:
Since Products
has no constructor that takes 0 arguments, you must create a constructor for FoodProducts
that calls the constructor of Products
will all the required arguments.
In C#, this is done like the following:
public class FoodProducts : Products
{
public FoodProducts(string id, string name, double price, int soldCount, int stockCount, double tax)
: base(id, name, price, soldCount, stockCount, tax)
{
}
public void Limit()
{
Console.WriteLine("This is an Attribute of a Product");
}
}
If you don't want to add this constructor to FoodProducts
, you can also create a constructor with no parameter to Products
.
Solution 3:
the constructor of the inherited class needs to construct the base class first. since the base class does not have a default constructor (taking 0 arguments) and you are not using the non-default constructor you have now, this won't work. so either A) add a default constructor to your base class, in which case the code of the descending class needs no change; or B) call the non-default constructor of the base class from the constructor of the descending class, in which case the base class needs no change.
A
public class Products
{
public Products() { }
}
public class FoodProducts : Products
{
public FoodProducts() { }
}
B
public class Products
{
public class Products(args) { }
}
public class FoodProducts : Products
{
public FoodProducts(args) : base(args) { }
}
some of this is explained rather OK on msdn here.
Solution 4:
As you inherit from Products
, you must call a base construct of Products
in your own class.
You didn't write:base(id, name, ....)
so C# assumes you call the default parameterless constructor, but it doesn't exist.
Create a default parameterless constructor for Products
.
Solution 5:
Just add
public Products()
{
}
in your products class And you will not get error
Reason: There exists a default constructor with 0 parameter for every class. So no need to define/write it explicitly (by programmer) BUT when you overload a default constructor with your desired number and type of parameters then it becomes a compulsion to define the default constructor yourself (explicitly) along with your overloaded constructor