C#：using和new关键字

1 using System;

1 using (SqlCommand cmd &＃61; new SqlCommand())
2 {
3 //执行代码
4 }

1 StringBuilder str &＃61; new StringBuilder();

1 public class Car
2 {
3 public string Name { get; set; }
4 public void PrintName()
5 {
6 Console.WriteLine($"this Car name is {Name}.");
7 }
8 }
9 public class FlyCar : Car
10 {
11 public new void PrintName() //隐藏基类中的PrintName()
12 {
13 Console.WriteLine($"this FlyCar name is {Name}.");
14 }
15 }

1 static void Main(string[] args)
2 {
3 FlyCar fyCar &＃61; new FlyCar();
4 fyCar.Name &＃61; "CoCo";
5 fyCar.PrintName(); //执行结果&＃xff1a;this FlyCar name is CoCo.
6 }

1 public class Car where T:new()
2 {
3 public T GetCar()
4 {
5 return new T();
6 }
7 }

1 public class Fish
2 {
3 public Fish() { }
4 }

1 static void Main(string[] args)
2 {
3 Car fish &＃61; new Car();
4 }