C#-筆記-基礎

String s = "123456";
Double d = Convert.ToDouble(s);//強制轉換變成double類型去進行運算
Double a = 12;
Double k = a + d;
Console.WriteLine("d={0},k={1}",d,a);//佔位符站好位置再寫
Console.ReadKey();

    Console.WriteLine("請輸入你的姓名");
    String name = Console.ReadLine();//接受用戶的字段
    Console.WriteLine("語文成績");
    String strChinese = Console.ReadLine();
    Console.WriteLine("數學成績");
    String strMath = Console.ReadLine();
    Double  Chinese = Convert.ToDouble(strChinese);
    Double Math = Convert.ToDouble(strMath);
    Console.WriteLine("姓名是{0}總成績是{1}平均成績是{2:0.00}", name, Chinese + Math, (Chinese + Math)/2); //這裡邊佔位符裡的2:0.00是取兩位小數的意思  

Int a , b = 2 ,c =3;
Int a = b++ * --c

/            //閏年判斷
            //可以被400整除
            //可以被4整除但是不能被100整除
            Console.WriteLine("請輸入年份");
            int year = Convert.ToInt32(Console.ReadLine());
            Boolean b = year % 400 == 0 || year % 4 == 0 && year % 100 == 0;
            Console.WriteLine(b);
            Console.ReadKey();

Console.WriteLine("請寫出一個數字");
            try
            {
                int b = Convert.ToInt32(Console.ReadLine());
                Console.WriteLine(b);
                Console.ReadKey();
            }
            catch {
                Console.WriteLine("輸入的數據有問題");
                Console.ReadKey();
            }

    //三元表達式
    Console.WriteLine("請輸入姓名");
    String name = Console.ReadLine();
    String result = name == "老趙" ? "人才" : "啥雕";
    Console.WriteLine(result);
    Console.ReadKey();

    //創建能產生隨機數的對象
    Random r = new Random();
    //讓產生隨機數的對象調用方法來產生隨機數
    for (int i = 0; i < 10; i++)
    {
        int rNumber = r.Next(1, 10);
        Console.WriteLine(rNumber);
    }
    Console.ReadKey();

常量的聲明語法：
//const 變量類型 變量名 = 值；
            //const 變量類型 變量名 = 值；
            const int num = 12;
            num = 21;
Error	1	The left-hand side of an assignment must be a variable, property or indexer	
错误 1 任务的左侧必须是变量、属性或索引器	
常量不能被改變；

[public] enum 枚舉名{值1，值2...}

namespace test02
{
    public enum Gender
    {
        男,
        女
    }
    class Program
    {
        static void Main(string[] args)
        {
            
            Gender gerder = Gender.男;
            Console.WriteLine(gerder);
            Console.ReadKey();下邊的括號就不寫了

[public] struct 結構名{成員變量}
與枚舉一樣放在命名空間裡
    public struct Person {
        public string _name;//一般在下邊放下劃線，以區別是字段不是變量
        public int _age;
        public char _gender;//加上public可以讓下邊方法來調用，不然權限不夠
    }

Person zsPerson;
            zsPerson.name = "張三";
            zsPerson.age = 32;
            zsPerson.gender = '男';
            Person lsPerson;
            lsPerson.name = "李四";
            lsPerson.age = 23;
            lsPerson.gender = '女';
            Console.WriteLine(zsPerson.name);
            Console.WriteLine(lsPerson.name);

    int[] num = { 1, 2, 3, 4, 5, 54, 7, 8, 9, 45 };
    int max = 0;
    int min = 21;
    for (int i = 0; i < num.Length;i++ )
    {
        if(max < num[i]){
            max = num[i];
        }
        if(min > num[i]){
            min = num[i];
        }
    }
    Console.WriteLine(max);
    Console.WriteLine(min);
    Console.ReadKey();//其實還是有缺陷的因為max，min不一定賦值的時候會出現問題所以給他一個初始值，這個初始值就是最小，int max = int.MinValue;在int範圍裡這個值最小。同理反之：int min = int.MinValue;  

在mian方法裡
            Console.WriteLine("輸入賬號");
            string uname = Console.ReadLine();
            Console.WriteLine("輸入密碼");
            string pwd = Console.ReadLine();
            string msg;
            bool b = Test(uname, pwd, out msg);
            Console.WriteLine("登錄結果是{0}",b);
            Console.WriteLine("登錄信息{0}",msg);
                    /// <summary>
        /// 驗證賬號密碼
        /// </summary>
        /// <param name="uname">用戶名</param>
        /// <param name="pwd">密碼</param>
        /// <param name="hh">返回值out語法</param>
        /// <returns>返回值字符串</returns>
        public static bool Test(string uname,string pwd,out string hh) {
            
            if(uname == "admin" && pwd == "admin"){
                hh = "登錄成功";
                return true;
            }
            if (uname == "admin")
            {
                hh = "賬號錯誤";
                return false;
            }
            else {
                hh = "其他錯誤，請從新輸入賬號密碼";
                return false;
            }

        }

			int n1 = 10;
            int n2 = 20;
            Test(ref n1,ref n2);
            Console.WriteLine("ni是{0}n2是{1}",n1,n2);
            #endregion
            Console.ReadKey();

 public static void Test(ref int n1,ref int n2) {
            int temp;
            temp = n1;
            n1 = n2;
            n2 = temp;
        }