using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace OverrideAndNew2 { class Program { static void Main(string[] args) { // Declare objects of the derived classes and test which version // of ShowDetails is run, base or derived. TestCars1(); // Declare objects of the base class, instantiated with the // derived classes, and repeat the tests. TestCars2(); // Declare objects of the derived classes and call ShowDetails // directly. TestCars3(); // Declare objects of the base class, instantiated with the // derived classes, and repeat the tests. TestCars4(); } public static void TestCars1() { System.Console.WriteLine("\nTestCars1"); System.Console.WriteLine("----------"); Car car1 = new Car(); car1.DescribeCar(); System.Console.WriteLine("----------"); // Notice the output from this test case. The new modifier is // used in the definition of ShowDetails in the ConvertibleCar // class. ConvertibleCar car2 = new ConvertibleCar(); car2.DescribeCar(); System.Console.WriteLine("----------"); Minivan car3 = new Minivan(); car3.DescribeCar(); System.Console.WriteLine("----------"); } // Output: // TestCars1 // ---------- // Four wheels and an engine. // Standard transportation. // ---------- // Four wheels and an engine. // Standard transportation. // ---------- // Four wheels and an engine. // Carries seven people. // ---------- public static void TestCars2() { System.Console.WriteLine("\nTestCars2"); System.Console.WriteLine("----------"); var cars = new List<car> { new Car(), new ConvertibleCar(), new Minivan() }; foreach (var car in cars) { car.DescribeCar(); System.Console.WriteLine("----------"); } } // Output: // TestCars2 // ---------- // Four wheels and an engine. // Standard transportation. // ---------- // Four wheels and an engine. // Standard transportation. // ---------- // Four wheels and an engine. // Carries seven people. // ---------- public static void TestCars3() { System.Console.WriteLine("\nTestCars3"); System.Console.WriteLine("----------"); ConvertibleCar car2 = new ConvertibleCar(); Minivan car3 = new Minivan(); car2.ShowDetails(); car3.ShowDetails(); } // Output: // TestCars3 // ---------- // A roof that opens up. // Carries seven people. public static void TestCars4() { System.Console.WriteLine("\nTestCars4"); System.Console.WriteLine("----------"); Car car2 = new ConvertibleCar(); Car car3 = new Minivan(); car2.ShowDetails(); car3.ShowDetails(); } // Output: // TestCars4 // ---------- // Standard transportation. // Carries seven people. } // Define the base class, Car. The class defines two virtual methods, // DescribeCar and ShowDetails. DescribeCar calls ShowDetails, and each derived // class also defines a ShowDetails method. The example tests which version of // ShowDetails is used, the base class method or the derived class method. class Car { public virtual void DescribeCar() { System.Console.WriteLine("Four wheels and an engine."); ShowDetails(); } public virtual void ShowDetails() { System.Console.WriteLine("Standard transportation."); } } // Define the derived classes. // Class ConvertibleCar uses the new modifier to acknowledge that ShowDetails // hides the base class method. class ConvertibleCar : Car { public new void ShowDetails() { System.Console.WriteLine("A roof that opens up."); } } // Class Minivan uses the override modifier to specify that ShowDetails // extends the base class method. class Minivan : Car { public override void ShowDetails() { System.Console.WriteLine("Carries seven people."); } } }
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