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  • c#语法练习8 函数

制作者:剑锋冷月 单位:无忧统计网,www.51stat.net
 

  无参、无返回值的函数:

using System;

class MyClass
{
  static void Show()
  {
    Console.WriteLine("function");
  }

  static void Main()
  {
    Show(); //function
    Console.ReadKey();
  }
}


		

 

  参数:

using System;

class MyClass
{
  static void Show(string str)
  {
    Console.WriteLine("is " + str);
  }

  static void Main()
  {
    show("function"); //is function
    Console.ReadKey();
  }
}


		

 

  返回值:

using System;

class MyClass
{
  static string Show(string str)
  {
    return "is " + str;
  }

  static void Main()
  {
    string s = Show("function");
    Console.WriteLine(s); //is function
    Console.ReadKey();
  }
}


		

 

  函数见 return 就返回:

using System;

class MyClass
{
  static int Math(int x, int y)
  {
    return x + y;
    return x * y; /* 执行不了这句 */
  }

  static void Main()
  {
    Console.WriteLine(Math(3,4)); //7
    Console.ReadKey();
  }
}


		

 

 

  数组参数:

using System;

class MyClass
{
  static int ArrMax(int[] arr)
  {
    int max = arr[0];
    for (int i = 1; i < arr.Length; i++)
      if (arr[i] > max) max = arr[i];
    return max;
  }

  static void Main()
  {
    int[] ns = { 1,2,3,4,5,4,3,2,1 };
    Console.WriteLine(ArrMax(ns));  //5
    Console.ReadKey();
  }
}


		

 

  参数数组(关键字 params):

using System;

class MyClass
{
  static int Sum(params int[] arr)
  {
    int count = 0;
    foreach(int i in arr) count += i;
    return count;
  }

  static void Main()
  {
    int n = Sum(1,2,3);
    Console.WriteLine(n);    //6

    n = Sum(1,2,3,4,5,6,7,8,9);
    Console.WriteLine(n);    //45

    Console.ReadKey();
  }
}


		

 

  引用参数和输出参数:

using System;

class MyClass
{
  static void proc1(ref int num)
  {
    num = num * num;
  }

  static void proc2(out int num)
  {
    num = 100;
  }

  static void Main()
  {
    int a = 9;
    proc1(ref a); /* 引用参数(ref) 参数必须是已初始化的 */
    Console.WriteLine(a); //81

    int b;
    proc2(out b); /* 输出参数类似 ref(但初始化不是必要的), 是从函数中接出一个值来 */
    Console.WriteLine(b); //100

    Console.ReadKey();
  }
}


		

 

 

  重载:

using System;

class MyClass
{
  static int Add(int n1, int n2)
  {
    return n1 + n2;
  }

  static string Add(string s1, string s2)
  {
    return s1 + s2;
  }

  static void Main()
  {
    Console.WriteLine(Add(111,222));   //333
    Console.WriteLine(Add("111", "222")); //111222

    Console.ReadKey();
  }
}


		

 

  委托(我觉得委托就是把函数当作一种类型的手段):

using System;

class MyClass
{
  delegate double MyFunType(double n1, double n2);

  static double Add(double n1, double n2) { return n1 + n2; }
  static double Dec(double n1, double n2) { return n1 - n2; }
  static double Mul(double n1, double n2) { return n1 * n2; }
  static double Div(double n1, double n2) { return n1 / n2; }

  static void Main()
  {
    MyFunType Fun;

    Fun = new MyFunType(Add); Console.WriteLine(Fun(3, 2)); // 5
    Fun = new MyFunType(Dec); Console.WriteLine(Fun(3, 2)); // 1
    Fun = new MyFunType(Mul); Console.WriteLine(Fun(3, 2)); // 6
    Fun = new MyFunType(Div); Console.WriteLine(Fun(3, 2)); // 1.5

    Console.ReadKey();
  }
}


		

 

 

  调用外部函数:

using System;
using System.Runtime.InteropServices;

class MyClass
{
  [DllImport("User32.dll")]
  public static extern int MessageBox(int h, string m, string c, int type);

  static void Main()
  {
    string str = "Visual Studio 2008!";
    MessageBox(0, str, "信息提示", 0);
  }
}


		

 

 

 

  数组参数:

using System;

class MyClass
{
  static int ArrMax(int[] arr)
  {
    int max = arr[0];
    for (int i = 1; i < arr.Length; i++)
      if (arr[i] > max) max = arr[i];
    return max;
  }

  static void Main()
  {
    int[] ns = { 1,2,3,4,5,4,3,2,1 };
    Console.WriteLine(ArrMax(ns));  //5
    Console.ReadKey();
  }
}


		

 

  参数数组(关键字 params):

using System;

class MyClass
{
  static int Sum(params int[] arr)
  {
    int count = 0;
    foreach(int i in arr) count += i;
    return count;
  }

  static void Main()
  {
    int n = Sum(1,2,3);
    Console.WriteLine(n);    //6

    n = Sum(1,2,3,4,5,6,7,8,9);
    Console.WriteLine(n);    //45

    Console.ReadKey();
  }
}


		

 

  引用参数和输出参数:

using System;

class MyClass
{
  static void proc1(ref int num)
  {
    num = num * num;
  }

  static void proc2(out int num)
  {
    num = 100;
  }

  static void Main()
  {
    int a = 9;
    proc1(ref a); /* 引用参数(ref) 参数必须是已初始化的 */
    Console.WriteLine(a); //81

    int b;
    proc2(out b); /* 输出参数类似 ref(但初始化不是必要的), 是从函数中接出一个值来 */
    Console.WriteLine(b); //100

    Console.ReadKey();
  }
}


		

 



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