A property that is MARKED with abstract KEYWORD is considered abstract property. An abstract property should not have any IMPLEMENTATION in the class. The derived classes must write their own implementation. In the example below FullName property is abstract in the Customer class. BankCustomer class overrides the INHERITED abstract FullName property with its own implementation.

using System;
abstract class Customer
{
private string _firstName = string.Empty;
private string _lastName = string.Empty;
public string FirstName
{
get
{
return _firstName;
}
set
{
_firstName = value;
}
}
public string LastName
{
get
{
return _lastName;
}
set
{
_lastName = value;
}
}
// FullName is abstract
public abstract string FullName
{
get;
}
}
class BankCustomer : Customer
{
// Overiding the FullName abstract property derived from customer class
public override string FullName
{
get
{
return "Mr. " + FirstName + " " + LastName;
}
}
}
class MAINCLASS
{
public static void Main()
{
BankCustomer BankCustomerObject = new BankCustomer();
BankCustomerObject.FirstName = "David";
BankCustomerObject.LastName = "Boon";
Console.WriteLine("Customer Full Name is : " + BankCustomerObject.FullName);
}
}

A property that is marked with abstract keyword is considered abstract property. An abstract property should not have any implementation in the class. The derived classes must write their own implementation. In the example below FullName property is abstract in the Customer class. BankCustomer class overrides the inherited abstract FullName property with its own implementation.

using System;
abstract class Customer
{
private string _firstName = string.Empty;
private string _lastName = string.Empty;
public string FirstName
{
get
{
return _firstName;
}
set
{
_firstName = value;
}
}
public string LastName
{
get
{
return _lastName;
}
set
{
_lastName = value;
}
}
// FullName is abstract
public abstract string FullName
{
get;
}
}
class BankCustomer : Customer
{
// Overiding the FullName abstract property derived from customer class
public override string FullName
{
get
{
return "Mr. " + FirstName + " " + LastName;
}
}
}
class MainClass
{
public static void Main()
{
BankCustomer BankCustomerObject = new BankCustomer();
BankCustomerObject.FirstName = "David";
BankCustomerObject.LastName = "Boon";
Console.WriteLine("Customer Full Name is : " + BankCustomerObject.FullName);
}
}