方法的结构
方法体内部代码的执行
本地变量
    类型推断和var关键字
    嵌套块中的本地变量
本地常量
控制流
方法调用
返回值
返回语句和void方法
参数
    形参
    实参
值参数
引用参数
引用类型作为值参数和引用参数
输出参数
参数数组
    方法调用
    用数组作为实参
参数类型总结
方法重载
命名参数
可选参数
栈帧
递归

int   MyMethod(int par1,string par2)
 ↑       ↑             ↑
 返回   方法           参数
 类型   名称           列表

static void Main()
{
    int myInt = 3;        //本地变量
    while(myInt > 0)      //控制流结构
    {
        --myInt;
        PrintMyMessage(); //方法调用
    }
}

static void Main()
{
    int myInt = 15;
    MyExcellentClass mec = new MyExcellentClass();
    ...
}

static void Main()
{
    var myInt = 15;
    var mec = new MyExcellentClass();
    ...
}

关键字
   ↓
const Type Identifier = Value;
                         ↑
                    初始化值是必须的

void SomeMethod()
{
    int intVal = 3;
    if(intVal == 3)
    {
        Console.WriteLine("Value is 3.");
    }
    for(int i=0;i<5;i++)
    {
        Console.WriteLine("Value of i:{0}",i);
    }
}

返回类型
  ↓
int GetHour()
{
    DateTime dt = DateTime.Now;
    int hour = dt.Hour;    //获取当前小时
    return hour;
       ↑
    返回语句
}

返回类型---MyClass
  ↓
MyClass method3()
{
    MyClass mc = new MyClass();
    ...
    return mc;
}

class MyClass
{
      ↓ void返回类型
    void TimeUpdate()
    {
        DateTime dt = DateTime.Now;
        if(dt.Hour<12)
            return;
        Console.WriteLine("It‘s afternoon!");
    }
    static void Main()
    {
        MyClass mc = new MyClass();
        mc.TimeUpdate();
    }
}

public void PrintSum(int x, float y)
{                         ↑
    ...                形参声明
}

class MyClass
{
    public int Val=20;
}
class Program
{
    static void MyMethod(MyClass f1,int f2)
    {
        f1.Val=f1.Val+5;
        f2=f2+5;
        Console.WriteLine("f1.val:{0},f2:{1}",f1.Val,f2);
    }
    static void Main()
    {
        MyClass a1=new MyClass();
        int a2=10;
        MyMethod(a1,a2);
        Console.WriteLine("f1.Val:{0},f2:{1}",a1.Val,a2);
    }
}

           包含ref修饰符
               ↓
void MyMethod(ref int val)
{
    ...
}
int y = 1;
MyMethod(ref y);
           ↑
      包含ref修饰符
MyMethod(ref 3+5);    //报错
           ↑
       必须使用变量

clas MyClass
{
    public int Val = 20;
}
class Program
{
                        ref修饰符        ref修饰符
                           ↓             ↓
    static void MyMethod(ref MyClass f1,ref int f2)
    {
        f1.Val=f1.Val+5;
        f2=f2+5;
        Console.WriteLine("f1.Val:{0},f2:{1}",f1.Val,f2);
    }
    static void Main()
    {
        MyClass a1=new MyClass();
        int a2 =10;
                   ref修饰符
                   ↓     ↓
        MyMethod(ref a1,ref a2);
        Console.WriteLine("f1.Val:{0},f2:{1}",a1.Val,a2);
    }
}

class MyClass{public int Val=20;}
class Program
{
    static void RefAsParameter(MyClass f1)
    {
        f1.Val=50;
        Console.WriteLine("After meber assignment:{0}",f1.Val);
        f1=new MyClass();
        Console.WriteLine("After new object creation:{0}",f1.Val);
    }
    static void Main()
    {
        MyClass a1=new MyClass();
        Console.WriteLine("Before method call:{0}",a1.Val);
        RefAsParameter(a1);
        Console.WriteLine("After method call:{0}",a1.Val);
    }
}

class MyClass{public int Val=20;}
class Program
{
    static void RefAsParameter(ref MyClass f1)
    {
        f1.Val=50;
        Console.WriteLine("After meber assignment:{0}",f1.Val);
        f1=new MyClass();
        Console.WriteLine("After new object creation:{0}",f1.Val);
    }
    static void Main(string[] args)
    {
        MyClass a1=new MyClass();
        Console.WriteLine("Before method call:{0}",a1.Val);
        RefAsParameter(ref a1);
        Console.WriteLine("After method call:{0}",a1.Val);
    }
}

class MyClass
{
    public int Val=20;
}
class Program
{
    static void MyMethod(out MyClass f1,out int f2)
    {
        f1=new MyClass();
        f1.Val=25;
        f2=15;
    }
    static void Main()
    {
        MyClass a1=null;
        int a2;
        MyMethod(out a1,out a2);
    }
}

void ListInts(params int[] inVals)
{...}

class MyClass
{
    public void ListInts(params int[] inVals)
    {
        if((inVals!=null)&&(inVlas.Length!=0))
        {
            for(int i=0;i<inVals.Length;i++)
            {
                inVals[i]=inVals[i]*10;
                Console.WriteLine("{0}",inVals[i]);
            }
        }
    }
}
class Program
{
    static void Main()
    {
        int first=5,second=6,third=7;
        MyClass mc=new MyClass();
        mc.ListInts(first,second,third);
        Console.WriteLine("{0},{1},{2}",first,second,third);
    }
}

class A
{
    long AddValues(int a,int b){return a+b;}
    long AddValues(int c int d,int e){return c+d+e;}
    long AddValues(float f,float g){return (long)(f+g);}
    long AddValues(long h,long m){return h+m;}
}

class B
{
    long AddValues(long a,long b){return a+b;}
    int AddValues(long c,long d){return c+d;}
}

class MyClass
{
    public int Calc(int a,int b,int c)
    {
        return (a+b)*c;
    }
    static void Main()
    {
        MyClass mc=new MyClass();
        int r0 = mc.Calc(4,3,2);
        int r1 = mc.Calc(4,b:3,c:2);
        int r2 = mc.Calc(4,c:2,b:3);
        int r3 = mc.Calc(c:2,b:3,a:4);
        int r4 = mc.Calc(c:2,b:1+2,a:3+1);
        Console.WriteLine("{0},{1},{2},{3},{4}",r0,r1,r2,r3,r4);
    }
}

class MyClass
{
    double GetCylinderVolume(double radius,double height)
    {
        return 3.1416*radius*radius*height;
    }
    static void Main(string[] args)
    {
        MyClass mc=new MyClass();
        double volume;
        volume = mc.GetCylindreVolume(3.0,4.0);
        ...
        volume = mc.GetCylindreVolume(radius:3.0,height:4.0)
    }
}

class MyClass
{
    public int Calc(int a ,int b=3)
    {
        return a+b;
    }
    static void Main()
    {
        MyClass mc=new MyClass();
        int r0=mc.Calc(5,6);
        int r1=mc.Calc(5);
        Console.WriteLine("{0},{1}",r0,r1);
    }
}

class MyClass
{
    public int Calc(int a=2,int b=3,int c=4)
    {
        return (a+b)*c;
    }
    static void Main()
    {
        MyClass mc=new MyClass();
        int r0=mc.Calc(5,6,7);
        int r1=mc.Calc(5,6);
        int r2=mc.Calc(5);
        int r3=mc.Calc();
        Console.WriteLine("{0},{1},{2},{3}",r0,r1,r2,r3);
    }
}

class MyClass
{
    double GetCylinderVolume(double radius=3.0,double height=4.0)
    {
        return 3.1416*radius*radius*height;
    }
    static void Main()
    {
        MyClass mc=new MyClass();
        double volume;
        volume =mc.GetCylindervoume(3.0,4.0)://位置参数
        Condole.WriteLine("Volume="+volume);
        volume =mc.GetCylindervoume(radius:2.0)://使用hieght默认参数
        Condole.WriteLine("Volume="+volume);
        volume =mc.GetCylindervoume(height:2.0)://使用radius默认参数
        Condole.WriteLine("Volume="+volume);
        volume =mc.GetCylindervoume()://使用默认值
        Condole.WriteLine("Volume="+volume);
    }
}

class Program
{
    static void MethodA(int par1,int par2)
    {
        Console.WriteLine("Enter MethodA:{0},{1}",par1,par2);
        MethodB(11,18);
        Console.WriteLine("Exit MethodA");
    }
    static void MethodB(int par1,int par2)
    {
        Console.WriteLine("Enter MethodB:{0},{1}",par1,par2);
        Console.WriteLine("Exit MethodB");
    }
    static void Main()
    {
        Console.WriteLine("Enter Main");
        MethodA(15,30);
        Console.WriteLine("Exit Main");
    }
}

class Program
{
    public void Count(int inVal)
    {
        if(inVal==0)
        {
            return;
        }
        else
        {
            Count(inVal-1);
            Console.WriteLine("{0}",inVal);
        }
    }
    static void Main()
    {
        Program pr=new Program();
        pr.Count(3);
    }
}