Class inherits from interface with extra property causes error

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I understand that interfaces don't allow fields. But why can't the class that implements the interface have a property/field. I have tried researching the cause of this, but to no avail. Could someone point me to a resource that can help me.

Can classes only implement the method they inherit from the interface and nothing else?

Here is my code:

using System;

interface IDog
{
    void Bark();
}

class Dog : IDog
{
    public int numberOfLegs = 24;
    public void Bark()
    {
        Console.WriteLine("Woof!");
    }
}

class Program
{
    static void Main()
    {
        IDog Fido = new Dog();
        Fido.Bark();
        Console.WriteLine("Fido has {0} legs", Fido.numberOfLegs);
    }
}

I get the error:

'IDog' does not contain a definition for 'numberOfLegs' and no extension method 'numberOfLegs' accepting a first argument of type 'IDog' could be found (are you missing a using directive or an assembly reference?)

asked 45 secs ago

TheLastGIS

44

Class inherits from interface with extra property causes error