C＃ Class Members
Class Members
Fields and methods inside classes are often referred to as "Class Members":
例子
Create a Car class with three class members: two fields 和one method.
// The class
class MyClass
{
// Class members
string color = "red"; // field
int maxSpeed = 200; // field
public void fullThrottle() // method
{
Console.WriteLine("The car is going as fast as it can!");
}
}
Fields
In the previous chapter, you learned that variables inside a class are called fields, and that you can access them by creating an object of the class, and by using the dot syntax (.).
The following example will create an object of the Car class, with the name myObj. Then we print the value of the fields color 和maxSpeed:
例子
class Car
{
string color = "red";
int maxSpeed = 200;
static void Main(string[] args)
{
Car myObj = new Car();
Console.WriteLine(myObj.color);
Console.WriteLine(myObj.maxSpeed);
}
}You can also leave the fields blank, and modify them when creating the object:
例子
class Car
{
string color;
int maxSpeed;
static void Main(string[] args)
{
Car myObj = new Car();
myObj.color = "red";
myObj.maxSpeed = 200;
Console.WriteLine(myObj.color);
Console.WriteLine(myObj.maxSpeed);
}
}This is especially useful when creating multiple objects of one class:
例子
class Car
{
string model;
string color;
int year;
static void Main(string[] args)
{
Car Ford = new Car();
Ford.model = "Mustang";
Ford.color = "red";
Ford.year = 1969;
Car Opel = new Car();
Opel.model = "Astra";
Opel.color = "white";
Opel.year = 2005;
Console.WriteLine(Ford.model);
Console.WriteLine(Opel.model);
}
}Object Methods
You learned from the C# 方法 chapter that methods are used to perform certain actions.
Methods normally belong to a class, and they define how an object of a class behaves.
Just like with fields, you can access methods with the dot syntax. However, note that the method must be public. And remember that we use the name of the method followed by two parentheses () and a semicolon ; to call (execute) the method:
例子
class Car
{
string color; // field
int maxSpeed; // field
public void fullThrottle() // method
{
Console.WriteLine("The car is going as fast as it can!");
}
static void Main(string[] args)
{
Car myObj = new Car();
myObj.fullThrottle(); // Call the method
}
}Why did we declare the method as public, and not static, like in the examples from the C# Methods Chapter?
The reason is simple: a static method can be accessed without creating an object of the class, while public methods can only be accessed by objects.
Use Multiple Classes
Remember from the last chapter that we can use multiple classes for better organization (one for fields and methods, and another one for execution). This is recommended:
prog2.cs
class Car
{
public string model;
public string color;
public int year;
public void fullThrottle()
{
Console.WriteLine("The car is going as fast as it can!");
}
}
prog.cs
class Program
{
static void Main(string[] args)
{
Car Ford = new Car();
Ford.model = "Mustang";
Ford.color = "red";
Ford.year = 1969;
Car Opel = new Car();
Opel.model = "Astra";
Opel.color = "white";
Opel.year = 2005;
Console.WriteLine(Ford.model);
Console.WriteLine(Opel.model);
}
}这 public keyword is called an access modifier, which specifies that the fields of Car are accessible for other classes as well, such as Program.
You will learn more about Access Modifiers in a later chapter.
Tip: As you continue to read, you will also learn more about other class members, such as constructors 和properties.
