上一小節的例子中，類A同時提供了不帶參數和帶參數的構造函數。
構造函數可以是不帶參數的，這樣對類的實例的初始化是固定的。有時，我們在對類進行實例化時，需要傳遞一定的數據，來對其中的各種數據初始化，使得初始化不再是一成不變的，這時，我們可以使用帶參數的構造函數，來實現對類的不同實例的不同初始化。
在帶有參數的構造函數中，類在實例化時必須傳遞參數，否則該構造函數不被執行。
讓我們回顧一下10.2節中關於車輛的類的代碼示例。我們在這裡添加上構造函數，驗證一下構造函數中參數的傳遞。
程序清單10-6:
using System;
class Vehicle //定義汽車類
{
public int wheels; //僅有成員：輪子個數
protected float weight; //保護成員：重量
public Vehicle(){;}
public Vehicle(int w,float g){
wheels=w;
weight=g;
}
public void Show(){
Console.WriteLine("the wheel of vehicle is:{0}",wheels);
Console.WriteLine("the weight of vehicle is:{0}",weight);
}
class train //定義火車類
{
public int num; //公有成員：車廂數目
private int passengers; //私有成員：乘客數
private float weight; //私有成員：重量
public Train(){;}
public Train(int n,int p,float w){
num=n;
passengers=p;
weight=w;
}
public void Show(){
Console.WriteLine("the num of train is:{0}",num);
Console.WriteLine("the weight of train is:{0}",weight);
Console.WriteLine("the Passengers train car is:{0}",Passengers);
}
}
class Car:Vehicle //定義轎車類
{
int passengers; //私有成員：乘客數
public Car(int w,float g,int p):base(w,g)
{
wheels=w;
weight=g;
passengers=p;
}
new public void Show(){
Console.WriteLine("the wheels of car is:{0}",wheels);
Console.WriteLine("the weight of car is:{0}",weight);
Console.WriteLine("the passengers of car is:{0}",Passengers);
}
}
class Test
{
public static void Main(){
Vehicle v1=new Vehicle(4,5);
Train t1=new Train();
Train t2=new Train(10,100,100);
Car c1=new Car(4,2,4);
v1.show();
t1.show();
t2.show();
c1.show();
}
}
程序的運行結果為：
the wheel of vehicle is :0
the weight of vehicle is:0
the num of train is:0
the weight of train is:0
the Passengers of train is:0
the num of train is:0
the weight of train is:0
the Passengers of train is:0
the wheel of car is:4
the weight of car is:2
the passengers of car is:4
