Duhok Polytechnic University Amedi Technical Institute/ IT Dept. Halkawt Rajab Hussain

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1 Duhok Polytechnic University Amedi Technical Institute/ IT Dept. By Halkawt Rajab Hussain

2 Inheritance: Concept of Inheritance. Types of inheritance. Virtual base class method. Interface. 4/1/2017 1

3 Concept of Inheritance: A One of the most important concepts in object-oriented programming is that of inheritance. Inheritance allows us to define a class in terms of another class, which makes it easier to create and maintain an application. This also provides an opportunity to reuse the code functionality and fast implementation time. When creating a class, instead of writing completely new data members and member functions, the programmer can designate that the new class should inherit the members of an existing class. This existing class is called the base class, and the new class is referred to as the derived class. The idea of inheritance implements the is a relationship. 4/1/2017 2

4 Inheritance: Inheritance in.net is defined with a special construct in the class declaration. In.NET and other modern programming languages, a class can inherit from a single class only (single inheritance), unlike C++ which supports inheriting from multiple classes (multiple inheritance). This limitation is necessitated by the difficulty in deciding which method to use when there are duplicate methods across classes (in C++, this problem is solved in a very complicated manner). In.NET, classes can inherit multiple interfaces. 4/1/2017 3

5 Syntax: The syntax used in C# for creating derived classes is as follows: : <acess-specifier> class <base_class>... class <derived_class> : <base_class>... 4/1/2017 4

6 Type of Inheritance: x x 4/1/2017 5

7 Type of Inheritance:(Single Inheritance) class A public void print() Console.WriteLine( Single Inheritance"); class B : A 4/1/2017 6

8 Type of Inheritance: (MultiLevel Inheritance) class A public void print() Console.WriteLine( MultiLevel Inheritance"); class B : A class C: B 4/1/2017 7

9 Type of Inheritance:(Hierarchical Inheritance) class A public void print() Console.WriteLine( Hierarchical Inheritance"); class B: A class C: A class D: A 4/1/2017 8

10 Example...Write a program in C# to find the result of following expression: y=2!+4!+ n! construct a class called fact represent as a super class contain operation to find factorial of any number and derived class from super class called sum to find the sumassion of all factorial numbers? namespace Expression class fact public int get_fact(int numf) int f = 1; for (int i = 2; i <= numf; ++i) f = f * i; return f; class sum : fact public int s; public void get_sum(int x) s = s + x; class Program static void Main(string[] args) sum sf = new sum(); int R = 5; for (int i = 2; i <= R; ++i) if (i % 2 == 0) sf.get_sum(sf.get_fact(i)); Console.WriteLine(sf.s); Console.ReadKey(); 4/1/2017 9

11 Class Diagram for the previous example. 4/1/

12 Virtual Base Class Methods: A virtual method is a method that can be redefined in derived classes. A virtual method has an implementation in a base class as well as derived the class. It is used when a method's basic functionality is the same but sometimes more functionality is needed in the derived class. A virtual method is created in the base class that can be overriden in the derived class. We create a virtual method in the base class using the virtual keyword and that method is overriden in the derived class using the override keyword 4/1/

13 Virtual Base Class Methods: Example namespace Virtual_methods public class abstructclass public virtual void mult() int x = 10*10; Console.WriteLine("defualt x= "+x); public class myclass: abstructclass class newclass: abstructclass public override void mult() int x = (10 * 10)*2; Console.WriteLine("new x= "+ x); class Program static void Main(string[] args) myclass m = new myclass(); m.mult(); newclass n = new newclass(); n.mult(); Console.ReadKey(); 4/1/

14 Interface.. An interface is defined as a syntactical contract that all the classes inheriting the interface should follow. The interface defines the 'what' part of the syntactical contract and the deriving classes define the 'how' part of the syntactical contract. Interfaces define properties, methods, and events, which are the members of the interface. Interfaces contain only the declaration of the members. It is the responsibility of the deriving class to define the members. It often helps in providing a standard structure that the deriving classes would follow 4/1/

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16 Example Interface with single class namespace Interface public interface Info void print(); void setinfo(string s, int a); public class std : Info string name; int a; public void setinfo(string n, int age) name = n; a = age; public void print() Console.WriteLine(name + " " + a); class Program static void Main(string[] args) std s = new std(); s.setinfo("ali", 30); s.print(); Console.ReadKey(); 4/1/

17 Example Single Class with two Interfaces(Multiple Inheritance) namespace Inheritance public interface Interface1 string Set_Data(string s); void Print(); public interface Interface2 void Display(); public class info : Interface1, Interface2 public string name; public string Set_Data(string s) name = s; return name; public void Display() Console.WriteLine("Interface2"); public void Print() Console.WriteLine(name); 4/1/

18 Thanks Any Questions 4/1/

Duhok Polytechnic University Amedi Technical Institute/ IT Dept. Halkawt Rajab Hussain

Duhok Polytechnic University Amedi Technical Institute/ IT Dept. By Halkawt Rajab Hussain 2016-04-02 Objects and classes: Basics of object and class in C#. Private and public members and protected. Static