c# 变量、运算符与类型转换

变量的定义与使用

//声明变量 ，即根据数据类型在内存申请空间            int age;            //给变量赋值，即将数据存储至对应的内存空间            age = 20;            //也可以同时给变量赋值            string name = "小王";            //使用变量既取出数据            Console.WriteLine("我叫" + name + "年龄" + age);

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常量的使用

  //常量的定义语法            //const 数据类型 常量名称 = 值；            const double PAI = 3.14;            double result = PAI * (5 * 5);            Console.WriteLine("圆的面积=" + result);

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枚举的使用

   Genders gender = Genders.Male;            Genders gender1 = Genders.dadsf;            Console.WriteLine((int)gender); //强制转换成整数            Console.WriteLine(gender1);        }             public enum Genders        {            Male = 0,            dadsf = 1        }

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控制台的使用

Console.WriteLine("输出后换行");            Console.WriteLine("这个也换行");            Console.WriteLine();            Console.Write("这个输出后不换行");            Console.Write("输出后真的不换行");            Console.ReadLine();

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格式化字符串输出

 string stuName = "张小熊"; //学员姓名            int stuAge = 20;            Console.WriteLine("学员姓名:{0} 年龄{1}", stuName, stuAge);            Console.ReadLine();

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从控制台读入信息

   Console.WriteLine("请输入姓名");            string studentName = Console.ReadLine();            Console.WriteLine("请输入年龄");            double age = Convert.ToDouble(Console.ReadLine());            Console.WriteLine("学员姓名:{0} 年龄{1}", studentName, age);            Console.ReadLine();

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运算符的使用

  int num1 = 50;            int num2 = 30;            int result = num1 + num2;            string a = "50";            string b = "30";            string result1 = a + b;            int result2 = result % 3;            int result3 = result / 3;            num1++;            num2--;            int result4 = num1 * num2;            Console.WriteLine(result);            Console.WriteLine(result1);            Console.WriteLine(result2);            Console.WriteLine(result3);            Console.WriteLine(result4);            Console.WriteLine(num1);

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前++ 后++

 int num1 = 50;            num1++;            ++num1;            Console.WriteLine(++num1); //前++ 加后再输出 = 53            Console.WriteLine(num1++);  //后++ 输出53  再++   输出的是53 但结果是54            Console.WriteLine(num1);   //结果是54

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数据类型的自动转换

 double a = 10.25;            int b = 20;            double result = a + b;            Console.WriteLine(result);

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数据类型的强制转换

double aa = 10.25;            int bb = 20;            int result1 = (int)aa + bb;            Console.WriteLine(result1);

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字符串和值类型的互相转换

 double a = double.Parse("20.5");            float b = float.Parse("11.2");            int c = int.Parse("20");            //值类型转换成字符串类型            string aa = a.ToString();            string bb = b.ToString();            string cc = c.ToString();            Console.WriteLine("aa={0},bb={1},cc={2}", aa, bb, cc);

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万能转换器的使用

 double a = Convert.ToDouble("20.5");            float b = Convert.ToSingle("12.5");            int c = Convert.ToInt32("20");            DateTime detetime = Convert.ToDateTime("1990-9-9");            int e = Convert.ToInt32(a);            int d = Convert.ToInt32(b);            double f = Convert.ToDouble(c);            Console.WriteLine("a={0},b={1},c={2},e={3},d={4},f={5}", a, b, c, e, d, f);

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浮点类型的字符串到int需要俩次强制转换

            int a = (int)double.Parse("35.8");            int b = (int)Convert.ToDouble("33.5");            Console.WriteLine("a={0},b={1}", a, b);