C# Virtual, Abstract and Overwrite－天天向上

virtual 虛擬方法，若希望或預料到基礎類別的這個方法在將來的衍生類別中會被覆寫（override），

則此方法必須被聲明為 virtual。

 1 class Employee
 2     {
 3         protected int m_salary;
 4         public virtual int Salary
 5         {
 6             get
 7             {
 8                 return m_salary;
 9             }
10             set
11             {
12                 if (value >= 22000 & value <= 42000)
13                 {
14                     m_salary = value;
15                 }
16                 else
17                 {
18                     if (value < 22000)
19                         m_salary = 22000;
20                     else
21                         m_salary = 42000;
22                 }
23             }
24         }
25         public void showTotal()
26         {
27             Console.WriteLine("實領薪水{0}", m_salary);
28         }
29     }

Operator薪水繼承Employee, 基本上薪水上下限的規則不變(與父類別相同)

 1 class Operator : Employee
 2     {
 3         public override int Salary
 4         {
 5             get
 6             {
 7                 return base.Salary;
 8             }
 9             set
10             {
11                 if (value >= 22000 & value <= 42000)
12                 {
13                     m_salary = value;
14                 }
15                 else
16                 {
17                     if (value < 22000)
18                         m_salary = 22000;
19                     else
20                         m_salary = 42000;
21                 }
22             }
23         }
24     }

 1     class Operator : Employee
 2     {
 3         public override int Salary
 4         {
 5             get
 6             {
 7                 return base.Salary;
 8             }
 9             set
10             {
11                 base.Salary = value;
12             }
13         }
14     }

Manager薪水繼承Employee, 但薪水上下限會覆寫以及多了紅利

 1 class Manager : Employee
 2     {
 3         public int Bonus { get; set; }
 4         public override int Salary
 5         {
 6             get
 7             {
 8                 return base.Salary;
 9             }
10             set
11             {
12                 if( (value >= 30000) && (value <=60000))
13                 {
14                     m_salary = value;
15                 }else
16                 {
17                     if (value < 30000)
18                     {
19                         m_salary = 30000;
20                     }
21                     else
22                     {
23                         m_salary = 60000;
24                     }
25                 }
26             }
27         }
28         public void showTotal()
29         {
30              Console.WriteLine("實領薪水{0}", Bonus + Salary);
31         }
32     }

測試

 1         static void Main(string[] args)
 2         {
 3             Manager Ryan = new Manager();
 4             Ryan.Salary = 70000;                // upper bound is 60000
 5             Ryan.Bonus = 30000;
 6             Console.WriteLine("Ryan's salary: ");
 7             Ryan.showTotal();
 8 
 9             Operator Peter = new Operator();
10             Peter.Salary = 18000;
11             Console.WriteLine("Peter's salary: ");
12             Peter.showTotal();
13             Console.Read();
14         }

====================================================================

abstract 抽象方法，是空的方法，沒有方法實體，衍生類必須以override 實現此方法。

1     public abstract class Employee
2     {
3         protected int m_salary;
4         public abstract int getSalary();
5         public abstract void setSalary(int value);
6         public abstract void showTotal();
7     }

Operator繼承Employee

 1     public class Operator : Employee
 2     {
 3         public override int getSalary()
 4         {
 5             return m_salary;
 6         }
 7         public override void setSalary(int value)
 8         {
 9             if (value >= 22000 & value <= 42000)
10             {
11                 m_salary = value;
12             }
13             else
14             {
15                 if (value < 22000)
16                     m_salary = 22000;
17                 else
18                     m_salary = 42000;
19             }
20         }
21         public override void showTotal()
22         {
23             Console.WriteLine("實領薪水{0}", m_salary);
24         }
25     }

Manager薪水繼承Employee, 但薪水上下限會覆寫以及多了紅利(Bonus)

 1     public class Manager : Employee
 2     {
 3         public int Bonus { get; set; }             
 4         public override int getSalary()
 5         {
 6             return m_salary;
 7         }
 8         public override void setSalary(int value)
 9         {
10             if (value >= 30000 & value <= 60000)
11             {
12                 m_salary = value;
13             }
14             else
15             {
16                 if (value < 30000)
17                     m_salary = 30000;
18                 else
19                     m_salary = 60000;
20             }
21         }
22         public override void showTotal()
23         {
24              Console.WriteLine("實領薪水{0}", m_salary+Bonus);
25         }
26     }

測試

 1 static void Main(string[] args)
 2         {
 3             Manager Ryan = new Manager();
 4             Ryan.setSalary(70000);
 5             Ryan.Bonus = 30000;
 6             Console.WriteLine("Ryan's salary: ");
 7             Ryan.showTotal();
 8 
 9             Operator Peter = new Operator();
10             Peter.setSalary(18000);
11             Console.WriteLine("Peter's salary: ");
12             Peter.showTotal();
13             Console.Read();
14         }