Esempio n. 1
0
 private static void DisplayWheterEqual(FoodClass food1, FoodClass food2)
 {
     if (food1 == food2)
     {
         Console.WriteLine(String.Format("{0,12} == {1}", food1, food2));
     }
     else
     {
         Console.WriteLine(String.Format("{0,12} != {1}", food1, food2));
     }
 }
        // When overriding Equals we also need to override GetHashCode and == (as good practive)
        public override bool Equals(object obj)
        {
            if (obj == null)
            {
                return(false);
            }
            if (ReferenceEquals(obj, this))
            {
                return(true);
            }
            if (obj.GetType() != this.GetType())
            {
                return(false);
            }

            FoodClass rhs = obj as FoodClass;

            return(_name == rhs._name && _group == rhs._group);
        }
Esempio n. 3
0
        static void Main(string[] args)
        {
            // 1) Standard Equal() method
            Food banana    = new Food("banana");
            Food chocolate = new Food("chocholate");

            Console.WriteLine(banana.Equals(chocolate)); //compare references
            Console.WriteLine(banana.Equals(null));      //compare references

            // 2) Static Equal() method
            Food exceptionFood = null; //will throw exception

            //Console.WriteLine(exceptionFood.Equals(chocolate));
            //Because of possible null value, we can use static Equal() from "object"
            Console.WriteLine(Equals(exceptionFood, chocolate));
            Console.WriteLine(Equals(chocolate, exceptionFood));
            Console.WriteLine(Equals(exceptionFood, exceptionFood));

            // 3) ReferenceEqual() method
            // Used to check wheter two variables refer to the same instance
            string bananaRef  = "banana";
            string banana2Ref = String.Copy(bananaRef);

            Console.WriteLine(ReferenceEquals(bananaRef, banana2Ref));
            Console.WriteLine(bananaRef.Equals(banana2Ref));

            // 4) Overriding Equality for value types (structs)
            FoodStruct foodStructBanana1 = new FoodStruct("banana", FoodGroup.Fruit);
            FoodStruct foodStructBanana2 = new FoodStruct("banana", FoodGroup.Fruit);
            FoodStruct foodStructCarrot  = new FoodStruct("carrot", FoodGroup.Vegetable);

            Console.WriteLine("banana == banana2: " + (foodStructBanana1 == foodStructBanana2));
            Console.WriteLine("banana2 == carrot: " + (foodStructBanana2 == foodStructCarrot));
            Console.WriteLine("carrot == banana: " + (foodStructCarrot == foodStructBanana1));

            // 5) Reference equality
            FoodClass       foodClass        = new FoodClass("apple", FoodGroup.Fruit);
            FoodClass       foodClass2       = new FoodClass("apple", FoodGroup.Fruit);
            CookedFoodClass cookedFoodClass  = new CookedFoodClass("stewed", "apple", FoodGroup.Fruit);
            CookedFoodClass cookedFoodClass2 = new CookedFoodClass("baked", "apple", FoodGroup.Fruit);
            CookedFoodClass cookedFoodClass3 = new CookedFoodClass("stewed", "apple", FoodGroup.Fruit);

            DisplayWheterEqual(foodClass, cookedFoodClass);
            DisplayWheterEqual(cookedFoodClass, cookedFoodClass2);
            DisplayWheterEqual(cookedFoodClass, cookedFoodClass3);
            DisplayWheterEqual(foodClass, foodClass2);
            DisplayWheterEqual(foodClass, foodClass);

            // 6) Comparison - implementation of IComparable<T> (not adviced to use in real world)
            CalorieCount cal300 = new CalorieCount(300);
            CalorieCount cal400 = new CalorieCount(400);

            DisplayOrder(cal300, cal400);
            DisplayOrder(cal400, cal300);
            DisplayOrder(cal300, cal300);
            if (cal300 < cal400)
            {
                Console.WriteLine("cal300 < cal400");
            }
            //In case of comparison operators, we should also implement == operator, Equals ect. (for developers convieniece)

            // 7) Comparer
            FoodClass[] list =
            {
                new FoodClass("orange", FoodGroup.Fruit),
                new FoodClass("banana", FoodGroup.Fruit),
                new FoodClass("apple",  FoodGroup.Fruit),
                new FoodClass("carrot", FoodGroup.Vegetable)
            };
            SortAndShowList(list);

            // 7) Comparer and inheritance
            FoodClass[] list2 =
            {
                new FoodClass("banana",    FoodGroup.Fruit),
                new FoodClass("apple",     FoodGroup.Fruit),
                new FoodClass("carrot",    FoodGroup.Vegetable),
                new CookedFoodClass("raw", "apple", FoodGroup.Fruit)
            };
            SortAndShowList(list2);
            FoodClass[] list3 =
            {
                new CookedFoodClass("raw", "apple",          FoodGroup.Fruit),
                new FoodClass("banana",    FoodGroup.Fruit),
                new FoodClass("apple",     FoodGroup.Fruit),
                new FoodClass("carrot",    FoodGroup.Vegetable)
            };
            SortAndShowList(list3);

            // 8) Equality comparer
            var foodItems = new HashSet <FoodStruct>(FoodStructEqualityComparer.Instance); // By default Equal in our struct is case sensitive, so HashSet treat it as different value. We provide Custom comparer to allo case insensitive comparison

            foodItems.Add(new FoodStruct("apple", FoodGroup.Fruit));
            foodItems.Add(new FoodStruct("pear", FoodGroup.Fruit));
            foodItems.Add(new FoodStruct("pineapple", FoodGroup.Fruit));
            foodItems.Add(new FoodStruct("Apple", FoodGroup.Fruit));
            foreach (var foodItem in foodItems)
            {
                Console.WriteLine(foodItem);
            }
        }