C# - 屬性

屬性是類、結構和介面的命名成員。類或結構中的成員變數或方法稱為欄位。屬性是欄位的擴充套件，並且使用相同的語法進行訪問。它們使用訪問器，透過訪問器可以讀取、寫入或操作私有欄位的值。

屬性不會命名儲存位置。相反，它們具有訪問器來讀取、寫入或計算其值。

例如，讓我們有一個名為 Student 的類，其中包含年齡、姓名和程式碼的私有欄位。我們無法從類範圍之外直接訪問這些欄位，但我們可以使用屬性來訪問這些私有欄位。

訪問器

屬性的訪問器包含幫助獲取（讀取或計算）或設定（寫入）屬性的可執行語句。訪問器宣告可以包含 get 訪問器、set 訪問器或兩者兼而有之。例如 -

// Declare a Code property of type string:
public string Code {
   get {
      return code;
   }
   set {
      code = value;
   }
}

// Declare a Name property of type string:
public string Name {
   get {
      return name;
   }
   set {
      name = value;
   }
}

// Declare a Age property of type int:
public int Age { 
   get {
      return age;
   }
   set {
      age = value;
   }
}

示例

以下示例演示了屬性的使用 -

using System;
namespace tutorialspoint {
   class Student {
      private string code = "N.A";
      private string name = "not known";
      private int age = 0;
      
      // Declare a Code property of type string:
      public string Code {
         get {
            return code;
         }
         set {
            code = value;
         }
      }
      
      // Declare a Name property of type string:
      public string Name {
         get {
            return name;
         }
         set {
            name = value;
         }
      }
      
      // Declare a Age property of type int:
      public int Age {
         get {
            return age;
         }
         set {
            age = value;
         }
      }
      public override string ToString() {
         return "Code = " + Code +", Name = " + Name + ", Age = " + Age;
      }
   }
   
   class ExampleDemo {
      public static void Main() {
      
         // Create a new Student object:
         Student s = new Student();
         
         // Setting code, name and the age of the student
         s.Code = "001";
         s.Name = "Zara";
         s.Age = 9;
         Console.WriteLine("Student Info: {0}", s);
         
         //let us increase age
         s.Age += 1;
         Console.WriteLine("Student Info: {0}", s);
         Console.ReadKey();
      }
   }
}

當以上程式碼編譯並執行時，會產生以下結果 -

Student Info: Code = 001, Name = Zara, Age = 9
Student Info: Code = 001, Name = Zara, Age = 10

抽象屬性

抽象類可能具有抽象屬性，該屬性應在派生類中實現。以下程式說明了這一點 -

using System;

namespace tutorialspoint {
   public abstract class Person {
      public abstract string Name {
         get;
         set;
      }
      public abstract int Age {
         get;
         set;
      }
   }
   class Student : Person {
      private string code = "N.A";
      private string name = "N.A";
      private int age = 0;
      
      // Declare a Code property of type string:
      public string Code {
         get {
            return code;
         }
         set {
            code = value;
         }
      }
      
      // Declare a Name property of type string:
      public override string Name {
         get {
            return name;
         }
         set {
            name = value;
         }
      }
      
      // Declare a Age property of type int:
      public override int Age {
         get {
            return age;
         }
         set {
            age = value;
         }
      }
      public override string ToString() {
         return "Code = " + Code +", Name = " + Name + ", Age = " + Age;
      }
   }
   
   class ExampleDemo {
      public static void Main() {
         // Create a new Student object:
         Student s = new Student();
         
         // Setting code, name and the age of the student
         s.Code = "001";
         s.Name = "Zara";
         s.Age = 9;
         Console.WriteLine("Student Info:- {0}", s);
         
         //let us increase age
         s.Age += 1;
         Console.WriteLine("Student Info:- {0}", s);
         Console.ReadKey();
      }
   }
}

當以上程式碼編譯並執行時，會產生以下結果 -

Student Info: Code = 001, Name = Zara, Age = 9
Student Info: Code = 001, Name = Zara, Age = 10