11.5.Encapsulating Type State with Properties
The practice of accessing field data via methods was good because it supported the object-oriented concept of encapsulation. For example, if the type of m_id or m_name changed from an int type to byte, calling code would still work. Now the same thing can be accomplished in a much smoother fashion with properties, as shown in Listing 10-2.
Listing 10-2. Accessing Class Fields With Properties
using System; publicclass Customer { privateint m_id = -1; publicint ID { get { return m_id; } set { m_id = value; } } privatestring m_name = string.Empty; publicstring Name { get { return m_name; } set { m_name = value; } } } publicclass CustomerManagerWithProperties { publicstaticvoid Main() { Customer cust = new Customer(); cust.ID = 1; cust.Name = "Amelio Rosales"; Console.WriteLine( "ID: {0}, Name: {1}", cust.ID, cust.Name); Console.ReadKey(); } }
Listing 10-2 shows how to create and use a property. The Customer class has the ID and Name property implementations. There are also private fields named m_id and m_name; which ID and Name, respectively, encapsulate. Each property has two accessors, get and set. The get accessor returns the value of a field. The set accessor sets the value of a field with the contents of value, which is the value being assigned by calling code. The value shown in the accessor is a C# reserved word.
When setting a property, just assign a value to the property as if it were a field. The CustomerManagerWithProperties class uses the ID and Name properties in the Customer class. The first line of Main instantiates a Customer object named cust. Next the value of the m_id and m_name fields of cust are set by using the ID and Name properties.
To read from a property, use the property as if it were a field. Console.WriteLine prints the value of the m_id and m_name fields of cust. It does this by calling the ID and Name properties of cust.
This was a read/write property, but you can also create read-only properties, which you’ll learn about next.