Course C# : C# and VB.NET / PDF
Course C# : C# and VB.NET / PDF
How would you implement inheritance using VB.NET/C#?
Server side code executes on the server.For this to occur page has to be submitted or posted back.Events fired by the controls are executed on the server.Client side code executes in the browser of the client without submitting the page.
e.g. In ASP.NET for webcontrols like asp:button the click event of the button is executed on the server hence the event handler for the same in a part of the code-behind (server-side code). Along the server-side code events one can also attach client side events which are executed in the clients browser i.e. javascript events.
How would you implement inheritance using VB.NET/C#?
Polymorphism is also achieved through interfaces. Like abstract classes, interfaces also describe the methods that a class needs to implement. The difference between abstract classes and interfaces is that abstract classes always act as a base class of the related classes in the class hierarchy. For example, consider a hierarchy-car and truck classes derived from four-wheeler class; the classes two-wheeler and four-wheeler derived from an abstract class vehicle. So, the class 'vehicle' is the base class in the class hierarchy. On the other hand dissimilar classes can implement one interface. For example, there is an interface that compares two objects. This interface can be implemented by the classes like box, person and string, which are unrelated to each other.
C# allows multiple interface inheritance. It means that a class can implement more than one interface. The methods declared in an interface are implicitly abstract. If a class implements an interface, it becomes mandatory for the class to override all the methods declared in the interface, otherwise the derived class would become abstract.
Can you explain what inheritance is and an example of when you might use it?
The savingaccount class has two data members-accno that stores account number, and trans that keeps track of the number of transactions. We can create an object of savingaccount class as shown below.
savingaccount s = new savingaccount ( "Amar", 5600.00f ) ;
From the constructor of savingaccount class we have called the two-argument constructor of the account class using the base keyword and passed the name and balance to this constructor using which the data member's name and balance are initialised.
We can write our own definition of a method that already exists in a base class. This is called method overriding. We have overridden the deposit( ) and withdraw( ) methods in the savingaccount class so that we can make sure that each account maintains a minimum balance of Rs. 500 and the total number of transactions do not exceed 10. From these methods we have called the base class's methods to update the balance using the base keyword. We have also overridden the display( ) method to display additional information, i.e. account number.
Working of currentaccount class is more or less similar to that of savingaccount class.
Using the derived class's object, if we call a method that is not overridden in the derived class, the base class method gets executed. Using derived class's object we can call base class's methods, but the reverse is not allowed.
Unlike C++, C# does not support multiple inheritance. So, in C# every class has exactly one base class.
Now, suppose we declare reference to the base class and store in it the address of instance of derived class as shown below.
account a1 = new savingaccount ( "Amar", 5600.00f ) ;
account a2 = new currentaccount ( "MyCompany Pvt. Ltd.", 126000.00f) ;
Such a situation arises when we have to decide at run-time a method of which class in a class hierarchy should get called. Using a1 and a2, suppose we call the method display( ), ideally the method of derived class should get called. But it is the method of base class that gets called. This is because the compiler considers the type of reference (account in this case) and resolves the method call. So, to call the proper method we must make a small change in our program. We must use the virtual keyword while defining the methods in base class as shown below.
public virtual void display( ) { }
We must declare the methods as virtual if they are going to be overridden in derived class. To override a virtual method in derived classes we must use the override keyword as given below.
public override void display( ) { }
Now it is ensured that when we call the methods using upcasted reference, it is the derived class's method that would get called. Actually, when we declare a virtual method, while calling it, the compiler considers the contents of the reference rather than its type.
If we don't want to override base class's virtual method, we can declare it with new modifier in derived class. The new modifier indicates that the method is new to this class and is not an override of a base class method.
How would you implement inheritance using VB.NET/C#?
When we set out to implement a class using inheritance, we must first start with an existing class from which we will derive our new subclass. This existing class, or base class, may be part of the .NET system class library framework, it may be part of some other application or .NET assembly, or we may create it as part of our existing application. Once we have a base class, we can then implement one or more subclasses based on that base class. Each of our subclasses will automatically have all of the methods, properties, and events of that base class ? including the implementation behind each method,
property, and event. Our subclass can add new methods, properties, and events of its own - extending the original interface with new functionality. Additionally, a subclass can replace the methods and properties of the base class with its own new
implementation - effectively overriding the original behavior and replacing it with new behaviors. Essentially inheritance is a way of merging functionality from an existing class into our new subclass. Inheritance also defines rules for how these methods, properties, and events can be merged. In VB.NET we can use implements keyword for inheritance, while in C# we can use the sign ( : ) between subclass and baseclass.......
How would you implement inheritance using VB.NET/C#?
Server side code executes on the server.For this to occur page has to be submitted or posted back.Events fired by the controls are executed on the server.Client side code executes in the browser of the client without submitting the page.
e.g. In ASP.NET for webcontrols like asp:button the click event of the button is executed on the server hence the event handler for the same in a part of the code-behind (server-side code). Along the server-side code events one can also attach client side events which are executed in the clients browser i.e. javascript events.
How would you implement inheritance using VB.NET/C#?
Polymorphism is also achieved through interfaces. Like abstract classes, interfaces also describe the methods that a class needs to implement. The difference between abstract classes and interfaces is that abstract classes always act as a base class of the related classes in the class hierarchy. For example, consider a hierarchy-car and truck classes derived from four-wheeler class; the classes two-wheeler and four-wheeler derived from an abstract class vehicle. So, the class 'vehicle' is the base class in the class hierarchy. On the other hand dissimilar classes can implement one interface. For example, there is an interface that compares two objects. This interface can be implemented by the classes like box, person and string, which are unrelated to each other.
C# allows multiple interface inheritance. It means that a class can implement more than one interface. The methods declared in an interface are implicitly abstract. If a class implements an interface, it becomes mandatory for the class to override all the methods declared in the interface, otherwise the derived class would become abstract.
Can you explain what inheritance is and an example of when you might use it?
The savingaccount class has two data members-accno that stores account number, and trans that keeps track of the number of transactions. We can create an object of savingaccount class as shown below.
savingaccount s = new savingaccount ( "Amar", 5600.00f ) ;
From the constructor of savingaccount class we have called the two-argument constructor of the account class using the base keyword and passed the name and balance to this constructor using which the data member's name and balance are initialised.
We can write our own definition of a method that already exists in a base class. This is called method overriding. We have overridden the deposit( ) and withdraw( ) methods in the savingaccount class so that we can make sure that each account maintains a minimum balance of Rs. 500 and the total number of transactions do not exceed 10. From these methods we have called the base class's methods to update the balance using the base keyword. We have also overridden the display( ) method to display additional information, i.e. account number.
Working of currentaccount class is more or less similar to that of savingaccount class.
Using the derived class's object, if we call a method that is not overridden in the derived class, the base class method gets executed. Using derived class's object we can call base class's methods, but the reverse is not allowed.
Unlike C++, C# does not support multiple inheritance. So, in C# every class has exactly one base class.
Now, suppose we declare reference to the base class and store in it the address of instance of derived class as shown below.
account a1 = new savingaccount ( "Amar", 5600.00f ) ;
account a2 = new currentaccount ( "MyCompany Pvt. Ltd.", 126000.00f) ;
Such a situation arises when we have to decide at run-time a method of which class in a class hierarchy should get called. Using a1 and a2, suppose we call the method display( ), ideally the method of derived class should get called. But it is the method of base class that gets called. This is because the compiler considers the type of reference (account in this case) and resolves the method call. So, to call the proper method we must make a small change in our program. We must use the virtual keyword while defining the methods in base class as shown below.
public virtual void display( ) { }
We must declare the methods as virtual if they are going to be overridden in derived class. To override a virtual method in derived classes we must use the override keyword as given below.
public override void display( ) { }
Now it is ensured that when we call the methods using upcasted reference, it is the derived class's method that would get called. Actually, when we declare a virtual method, while calling it, the compiler considers the contents of the reference rather than its type.
If we don't want to override base class's virtual method, we can declare it with new modifier in derived class. The new modifier indicates that the method is new to this class and is not an override of a base class method.
How would you implement inheritance using VB.NET/C#?
When we set out to implement a class using inheritance, we must first start with an existing class from which we will derive our new subclass. This existing class, or base class, may be part of the .NET system class library framework, it may be part of some other application or .NET assembly, or we may create it as part of our existing application. Once we have a base class, we can then implement one or more subclasses based on that base class. Each of our subclasses will automatically have all of the methods, properties, and events of that base class ? including the implementation behind each method,
property, and event. Our subclass can add new methods, properties, and events of its own - extending the original interface with new functionality. Additionally, a subclass can replace the methods and properties of the base class with its own new
implementation - effectively overriding the original behavior and replacing it with new behaviors. Essentially inheritance is a way of merging functionality from an existing class into our new subclass. Inheritance also defines rules for how these methods, properties, and events can be merged. In VB.NET we can use implements keyword for inheritance, while in C# we can use the sign ( : ) between subclass and baseclass.......
Course C# : C# and VB.NET / PDF
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