c#基础学习强化

很久没有学习c#的一些基础知识了，发现自己的桌面上下了一本c#完全手册的书，于是从简入难，再会回顾一下基础知识，温故而知新嘛。

本文纯粹是学习记录，大部分无原创成分，如有侵权请告知。

--- c# 传值:

如果是值参数，swap不能实现换值:

static void Swap(int x, int y)
{
int temp = x;
x = y;
y = temp;

}
static void Main()
{
int i = 1, j = 2;
Swap(i,j);
Console.WriteLine("i={0},j={1}",i,j);
}
返回 :  i=1,j=2

----c# 传址

引用型参数以ref修饰声明:

static void Swap(ref int x, ref int y)
{
int temp = x;
x = y;
y = temp;
}
static void Main()
{
int i = 1, j = 2;
Swap(ref i, ref j);
Console.WriteLine("i={0},j={1}", i, j);
}
返回值: i=2,j=1

---- 输出型参数:

输出型参数加out

string s;
void F(ref string a, ref string b)
{
s = "1";
a = "2";
b = "3";
}
void G()
{
F(ref s, ref s);
}

static void SplitPath(string path, out string dir, out string name)
{
int i = path.Length;
while (i > 0)
{
char ch = path[i - 1];
if (ch == '\\' || ch == '/' || ch == ':') break;
i--;
}
dir = path.Substring(0, i);
name = path.Substring(i);
}
static void Main()
{
string dir, name;
SplitPath("c:\\Temp\\test1.xls", out dir, out name);
Console.WriteLine(dir);
Console.WriteLine(name);
}

--- 数组类型的参数:

args用法; 循环些数组的方法: foreach(int i in args) Console.Write("{0}",i);

static void F(params int[] args)
{
Console.WriteLine("Array contains {0} elements:", args.Length);
foreach (int i in args) Console.Write("{0}",i);
Console.WriteLine();
}
public static void Main()
{
int[] a ={ 1, 2, 3 };
F(a);
F(10,20,30,40);
F();
}

--- 类的声明和调用例子:

class Student
{
public string s_name;
public int s_age;
public float s_weight;
public Student(string n, int a, float w)
{
s_name = n;
s_age = a;
s_weight = w;
}
public int max_age(int x, int y)
{
if (x > y) return x;
else return y;
}
public float max_weight(float x, float y)
{
if (x > y) return x;
else return y;
}
}
class Test
{
public static void Main()
{
Student s1 = new Student("Mike", 21, 70);
Student s2 = new Student("John", 21, 70);
if (s1.max_age(s1.s_age, s2.s_age) == s1.s_age)
Console.WriteLine("{0}'s age is bigger than {1}'s", s1.s_name, s2.s_name);
else
Console.WriteLine("{0}'s age is bigger than {1}'s", s1.s_name, s2.s_name);
if (s1.max_weight(s1.s_weight, s2.s_weight) == s1.s_weight)
Console.WriteLine("{0}'s age is weighter than {1}'s", s1.s_name, s2.s_name);
else
Console.WriteLine("{0}'s age is weighter than {1}'s", s1.s_name, s2.s_name);

}
}

---- 类的声明和调用，还有方法的重载:

class Student
{
public string s_name;
public int s_age;
public float s_weight;

public Student(string n,int a, float w)
{
s_name  = n;
s_age = a;
s_weight = w;
}
public float max(float x, float y)
{
if (x > y) return x;
else return y;
}
public int max(int x, float y)
{
if (x > y) return x;
else return y;
}
}
class Test
{
public static void Main()
{
Student s1 = new Student("Mike",21,70);
Student s2 = new Student("John",21,70);
if (s1.max(s1.s_age, s2.s_age) == s1.s_age)
Console.WriteLine("{0}'s age is bigger than {1}'s", s1.s_name, s2.s_name);
else
Console.WriteLine("{0}'s age is smaller than {1}'s", s1.s_name, s2.s_name);
if (s1.max(s1.s_weight, s2.s_weight) == s1.s_weight)
Console.WriteLine("{0}'s weight is bigger than {1}'s", s1.s_name, s2.s_name);
else
Console.WriteLine("{0}'s weight is smaller than {1}'s", s1.s_name, s2.s_name);
}
}

---- 构造函数与析构函数;

构造函数是在初始化类和实例的时候第一个开始调用的:

如果缺省，系统自动创建;

class Vehicle
{
public int wheels;
protected float weight;
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
{
public int num;
private int passeners;
private float weight;
public train(){;}
public train(int n,int p,float w)
{
num = n;
passeners = p;
weight = w;
}
public void show()
{
Console.WriteLine("the number of train is :{0}", num);
Console.WriteLine("the weight of train is :{0}", weight);
Console.WriteLine("the number of passenger is :{0}", passeners);
}
}
class car : Vehicle
{
int passengers;
public car(int w, float g, int p)
: base(w, g)
{
wheels = w;
weight = g;
passengers = p;
}
new public void show()
{
Console.WriteLine("the wheel 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();
}
}

--- 编辑操作符:

作用就是定义一种操作符来批量修改类里面的属性.

class player
{
public int neili;
public int tili;
public int jingyan;
public int neili_r;
public int tili_r;
public player()
{
neili = 10;
tili = 50;
jingyan = 0;
neili_r = 50;
tili_r = 50;
}
public static player operator ++(player p)
{
p.neili = p.neili + 50;
p.tili = p.tili + 100;
p.neili_r = p.neili;
p.tili_r = p.tili;
return p;
}
public void show()
{
Console.WriteLine("Tili:{0}", tili);
Console.WriteLine("Jingyan:{0}", jingyan);
Console.WriteLine("Neili:{0}", neili);
Console.WriteLine("Tili_full:{0}", tili_r);
Console.WriteLine("Neili_full:{0}", neili_r);
}
class Test
{
public static void Main() {
player man = new player();
man.show();
man++;
Console.WriteLine("Now upgrading ....");
man.show();
}
}
}

---- 杨辉三角，用二维数组实现:

static void Main(string[] args)
{
int[,] a = new int[5, 5];
a[0, 0] = 1;
for (int i = 1; i < 5; i++)
{
a[i, 0] = 1;
a[i, i] = 1;
for (int j = 1; j < i; j++)
{
a[i, j] = a[i - 1, j - 1] + a[i - 1, j];
}
}
for (int i = 0; i < 5; i++)
{
for (int j = 0; j <= i; j++)
{
Console.Write("{0}",a[i,j]);
}
Console.WriteLine();
}
}

输出结果如下:

1

11

121

1331

14641

+++ 静态类和非静态类区别:

静态域申明: static修饰符，不加则为非静态域； 静态域和非静态域分数静态变量与非静态变量; 静态域无论建立多少该类的实例，内存中只有一个静态数据拷贝，所以当这个的第一个实例建立时，域被初始化，以后在创建新对象时就不需要再做初始化了. 非晶态类实例化相反，每次都要创建一份单独的拷贝。