20190404-C#學習日誌

// LINQ

//架構
// from
// where
// select
// using System.Linq

int [] numbers = {0, 1, 2, 3, 4, 5, 6};

var evenNumQuery =
     from num in numbers
     where (num % 2 == 0)
     select num;

foreach(int i in evenNumQuery)
{
     Console.WriteLine("{0} is an even number", i);
}

/*--------------------------------------------------------------------------------------------------*/

using System.Linq
using System.Collections.Generic

public static void Main(string [] args)
{
     List<Customer> customers = new List<Customer>();
     customers.Add(new Customer("Alan", 25.60));
     customers.Add(new Customer("Bill", -32.1));
     customers.Add(new Customer("Carl", -12.2));
     customers.Add(new Customer("David", 12.6));

     var overdue =
     from cust in customers
     where cust.Balance < 0

     //排列，並且從小排到大
     orderby cust.Balance ascending

     //排列，並且從大排到小
     //orderby cust.Balance descending
    
     //選擇多個屬性
     select new{cust.Name, cust.Balance};

     foreach(var cust in overdue)
     {
          Console.WriteLine("Name = {0}, Balance = {1}", cust.Name, cust.Balance)
     }
}

20190331-C#學習日誌

//枚舉Enum

enum DaysOfWeek
{
     Sun, Mon, Tues, Wed, Thurs, Fri, Sat
}

// Tues後面未指定，將從前一個值累加
enum DaysOfWeek2
{
     Sun = 5, Mon = 10, Tues, Wed, Thurs, Fri, Sat
}

// enum預設為 int(整數)型態, 可用以下方是將enum改為別的型態
enum DaysOfWeek3 : byte
{
     Sun = 5, Mon = 10, Tues, Wed, Thurs, Fri, Sat
}

public static void Main(string [] args)
{
     DaysOfWeek myDays = DayOfWeek.Mon;
     Console.WriteLine((int)myDays); // 1
     Console.WriteLine((DaysOfWeek)1); // Mon
}

/*--------------------------------------------------------------------------------------------------*/

// struct 結構

//不支援繼承

// class為引用類型, structs 為值類型

struct MyStruct
{
     private int x, y;
     private AmotherClass myclass;
     private Days myDays;

     public MyStruct(int a, int b, int c)
     {
          myClass = new AnotherClass();
          myClass.number = a;
          x = b;
          y = c;
          myDays = Days.Mon
     }

     public void PrintStatement()
     {
          Console.WriteLine("x = {0}, y = {1}, myDays = {2}", x, y, myDays);
     }

     enum Days {Mon, Tues, Wed}
     class AnotherClass
     {
          public int number;
     }
}

public static void Main(string [] args)
{
     MyStruct example = new MyStruct(2, 3, 5);
     example.PrintStatement();
}

20190330-C#學習日誌

// params 當不知道有多少參數

public void PrintDestinations(params string [] destinations)
{
      for(int i = 0; i < destinations.Length; i++)
     {
          Console.WriteLine(destinations[i] + " ");
     }
}

/*--------------------------------------------------------------------------------------------------*/

//繼承

//保護的(只有同個class與繼承的class可使用的)

class Member
{
     //受保護的(同一個class 與 繼承class可使用的)
     protected int annualFee;

     private string name;
     private int memberId;
     private int memberSince;

     public Member()
     {
          Console.WriteLine("Parent Constructor with no parameter");
     }

     public Member(string pName, int pMemberId, int pMemberSince)
     {
          Console.WriteLine("Parent Constructor with three parameters");
          name = pName;
          memberId = pMemberId;
          memberSince = pMemberSince;
     }

     public override string ToString()
     {
          return "\nName: " + name + "\nMember ID: " + memberId +
                    "\nMember since: " + memberSince +
                    "\nTotal Annual Fee: " + annualFee;
     }

     //可被子類重新寫
     public virtual void CalculateAnnualFee()
     {
          annualFee = 0;
     }
}

//繼承父類

class NormalMember : Member
{
     public NormalMember()
     {
          Console.WriteLine("Chind constructor with no parameter");
     }

     public NormalMember(string remarks, string name, int memberId, int memberSince)
         :base(name, memberId, memberSince)
     {
          Console.WriteLine("Child constructor with 4 parameters");
          Console.WriteLine("Remarks = {0}", remarks);
     }

     publice override void CalculateAnnualFee()
     {
          //從父類繼承的變數
          annualFee = 100 + 12 * 30;
     }
}

//主程序
publice static void Main(string [] args)
{
     Member [] clubMembers = new Member[5];
    
     clubMembers[0] = new NormalMember("Special Rate", "James", 1, 2010);
     clubMembers[1] = new NormalMember("Normal Rate", "Andy", 2, 2011);
     clubMembers[2] = new NormalMember("Normal Rate", "Bill", 3, 2011);
     clubMembers[3] = new VIPMember("Carol", 4, 2011);
     clubMembers[4] = new VIPMember("Evelyn", 5, 2011);

     foreach(Member m in clubMembers)
     {
          m.CalculateAnnualFee();
          Console.WriteLine(m);
     }
}

//繼承父類

class VIPMember : Member
{
     public VIPMember(string name, int memberId, int memberSince)
         :base(name, memberId, memberSince)
     {
          Console.WriteLine("Child constructor with 3 parameters");
     }

     public override void CalculateAnnualFee()
     {
          annualFee = 1200;
     }
}

/*--------------------------------------------------------------------------------------------------*/

// GetType() 和 typeof()

// GetType() 返回目標運行時的類型

// typeof() 接受一個類型名稱
 

20190326-C#學習日誌

//聲明結構
//需與Class名稱相同

class Staff
{
     public Staff(string name)
     {
          nameOfStaff = name;
          Console.WriteLine("\n" + nameOfStaff);
          Console.WriteLine("--------------------------------------------------");
     }
     public Staff(string firstName, string lastName)
     {
          nameOfStaff = firstName + " " + lastName;
          Console.WriteLine("\n" + nameOfStaff);
          Console.WriteLine("--------------------------------------------------");      }
}

/*--------------------------------------------------------------------------------------------------*/

public static void Main(string [] args)
{
     //將Class實例化
     Staff staff1 = new Staff("Peter");

     //使用Class中的屬性或者方法
     staff1.HoursWorked = 160;

     int pay = staff1.CalculatePay(1000, 400);

     Console.WriteLine("Pay = {0}", pay);

     Staff staff2 = new Staff("John", "Tan")
     staff2 = HoursWorked = 160;
     pay = staff2.CalculatePay();
     Console.WriteLine("Pay = {0}", pay);

     Staff staff3 = new Staff("Carol");
     staff3 = HoursWorked = -10;
     pay = staff3.CalculatePay();
     Console.WriteLine("Pay = {0}", pay);
}

/*--------------------------------------------------------------------------------------------------*/

//在螢幕列印出ToString的方法
Console.WriteLine(staff1);

//如果沒有複寫ToString
//列印出螢幕時只會顯示namespace 與 class名稱

/*--------------------------------------------------------------------------------------------------*/

//聲明靜態方法

public static double convertMilesToKilometers(double miles)
{
     return miles * 1.60934;
}

/*--------------------------------------------------------------------------------------------------*/

//宣告方法，接受類型為Arrary 和 List

public void PrintFirstDestination(string [] destinations)
{
     Console.WriteLine("This first destination is {0}. \n", destinations[0]);
}

public void PrintFirstDestination(List<string> destinations)
{
     Console.WriteLine("This first destination is {0}. \n", destinations[0]);
}

//將屬性return 為 Arrary 或 List
public List<string> returnDestinations
{
     get
     {
          return destinations;
     }
}

public string [] returnDestinations
{
     get
     {
          return destinations;
     }
}

20190325-C#學習日誌

// For Loop

for(int i = 0; i < 5; i++)
{
     Console.WriteLine(i);
}

int [] myNumbers = {10, 20, 30, 40, 50};

for(int i = 0; i < myNumbers.Length; i++)
{
     Console.WriteLine(myNumbers[i]);
}

/*--------------------------------------------------------------------------------------------------*/

// Foreach Loop

char [] message = {'H', 'e', 'l', 'l', 'o'};

foreach(char i in message)
{
     Console.WriteLine(i);
}

/*--------------------------------------------------------------------------------------------------*/

// While

int counter = 5;

while(counter > 0)
{
     Console.WriteLine("Counter = {0}", counter);
     counter--;
}

/*--------------------------------------------------------------------------------------------------*/

// Do while

int counter = 100;

do
{
     Console.WriteLine("Conter = {0}", counter);
     counter++;
}
while (counter < 0);

/*--------------------------------------------------------------------------------------------------*/

// break

for(int i = 0; i < 5; i++)
{
     Console.WriteLine("i = {0}", i);
     if(i == 2)
     break;
}

/*--------------------------------------------------------------------------------------------------*/

// continue

for(int i = 0; i < 5; i++)
{
     Console.WriteLine("i = {0}", i);
     if(i == 2)
           continue;
     Console.WriteLine("I will not be printed if i = 2.\n");
}

/*--------------------------------------------------------------------------------------------------*/

//異常處理 Exception Handing

int numerator, denominator;

Console.Write("Please enter numerator: ");
numerator = Convert.ToInt32(Console.ReadLine());

Console.Write("Please enter denominator: ");
denominator = Convert.ToInt32(Console.ReadLine());

try //嘗試
{
     Console.WriteLine("The result is {0}", numerator / denominator);
}
catch(Exception e) //例外的處理方法
{
     Console.WriteLine(e.Message);
}
finally //不論是否發生例外都會執行
{
     Console.WriteLine("--- End of Error Handling Example ---");
}

/*--------------------------------------------------------------------------------------------------*/

//特定異常處理


catch(DivideByZeroException e) //除數等於零
{
     Console.WriteLine(e.Message);
}

int numerator, denominator;

try
{
     Console.Write("Please enter numerator: ");
     numerator = Convert.ToInt32(Console.ReadLine());

     Console.Write("Please enter denominator: ");
     denominator = Convert.ToInt32(Console.ReadLine());
}
catch(FormatException e)
{
     Console.WriteLine("Error: You did not enter an integer");
}
catch(DivideByZeroException)
{
     Console.WriteLine(e.Message);
}

/*--------------------------------------------------------------------------------------------------*/

 //聲明屬性

private  string nameOfStaff;
private const int hourlyRate = 30;
private int hWorked;

public int HoursWorked
{
     get
     {
          return hWorked;
     }
     set
     {
          if(value > 0)
          {
               hWorked = value;
          }
          else
          {
               hWorked = 0;
          }
     }
}

//如果沒有任何邏輯，可以使用以下簡短資料
public int HoursWorked {get; set;}

/*--------------------------------------------------------------------------------------------------*/

//聲明方法

public void PrintMessage()
{
     Console.WriteLine("Calculating Pay...");
}

public int CalculatePay()
{
     PrintMessage();

     int staffPay;
     staffPay = hWorked * hourlyRate;

     if(hWorked > 0)
          return staffPay;
     else
          return 0;
}

/*--------------------------------------------------------------------------------------------------*/

// C#允許不同方法使用同名(參數需不同)

public int CalculatePay()
{
     PrintMessage();

     int staffPay;
     staffPay = hWorked * hourlyRate;

     if(hWorked > 0)
          return staffPay;
     else
          return 0;
}

publice int CalculatePay(int bonus, int allowance)
{
     PrintMessage();

     int staffPay;
     staffPay = hWorked * hourlyRate + bonus + allowance;

     if(hWorked > 0)
          return staffPay;
     else
          return 0;
}

/*--------------------------------------------------------------------------------------------------*/

// ToString()的方法

//重寫方法 override

public override string ToString()
{
     return "Name of Staff = " + nameOfStaff + " Hour Rate = " + hourlyRate +
     " Hours Worked = " + hWorked;
}

20190324-C#學習日誌

//自動換行
Console.WriteLine("Hello ");

Console.WriteLine("How are you?");

//不會自動換行

Console.Write("Hello ");

Console.Write("How are you?");

//如果開頭加入
using static System.Console;

//將不必再輸入Console

WriteLine("Hello ");

WriteLine("How are you?");

//將變數列印到螢幕中

int userAge = 30;

Console.WriteLine(userAge);

//連接字串並列印到螢幕中

Console.WriteLine("Hello, " + "how are you?" + " I love C#.");

int results = 79;
Console.WriteLine("You scored " + results + " marks for your test.");

Console.WriteLine("You scored {0} marks for your test. {1}", results, "Congratulations!");

Console.WriteLine("You scored {0:F3} marks for yout test.", 123.45678);

Console.WriteLine("You have {0:C} dollars.", 2111);

/*--------------------------------------------------------------------------------------------------*/

//跳脫字元

//Tab
Console.WriteLine("Hello\tWorld");

//換行
Console.WriteLine("Hello\nWorld");

//顯示\
Console.WriteLine("\\");

//顯示"
Console.WriteLine("\"Hello!\"");

/*--------------------------------------------------------------------------------------------------*/

//接受用戶輸入字串

String userInput = Console.ReadLine();

Console.WriteLine(userInput);

/*--------------------------------------------------------------------------------------------------*/

//將字串轉換為數值

String userInput = Console.ReadLine();

int newUserInput = Convert.ToInt32(userInput);

newUserInput++;

Console.WriteLine(newUserInput);

/*--------------------------------------------------------------------------------------------------*/

//之前的總結

using System;

namespace HelloWorld
{
    class MainClass
         public static void Main(string [] args)
         {
              string userName = "";
              int userAge = 0;
              int currentYear = 0;
 
              Console.WriteLine("Please enter your name: ");
              userName = Console.ReadLine();
 
              Console.WriteLine("Please enter your age: ");
              userAge = Convert.ToInt32(Console.ReadLine());
 
              Console.WriteLine("Please enter current year: ");
              currentYear = Convert.ToInt32(Console.ReadLine());

              Console.WriteLine("Hello World! My name is {0} and I am {1} " +
              "I was born in {2}.",
              userName, userAge,  currentYear - userAge);
         }
    }
}

/*--------------------------------------------------------------------------------------------------*/

// If and else

using System;

namespace HelloWorld
{
     class MainClass
     {
          public static void Main(string [] args)
          {
                int userAge = 0;
 
                Console.WriteLine("Please enter your age: ");
                userAge = Convert.ToInt32(Console.ReadLine());
 
                if( userAge < 0 || userAge > 100)
                {
                     Console.WriteLine("Invalid Age.");
                     Console.WriteLine("Age must be between 0 and 100.");
                }
                else if(userAge < 18)
                {
                     Console.WriteLine("Sorry, you are underage.");
                }
                else if(userAge < 21)
                {
                     Console.WriteLine("You need parental consent.");
                }
                else
                {
                     Console.WriteLine("Congratulations! You may sign up!");
                }
          }
     } }

/*--------------------------------------------------------------------------------------------------*/

// Switch

using System;

namespace HelloWorld
{
     class MainClass
     {
          public static void Main()
          {
               Console.WriteLine("Enter your grade:");
               string userGrade = Console.ReadLine();

               switch(userGrade)
               {
                    case "A":
                         Console.WriteLine("Distinction");
                         break;
                    case "B":
                         Console.WriteLine("B Grade");
                         break;
                    case "C":
                         Console.WriteLine("C Grade");
                         break;
                    default:
                         Console.WriteLine("Fail");
                         break;
               }
          }
     }
}

20190322-C#學習日誌

using System; //使用System的命名空間

/*--------------------------------------------------------------------------------------------------*/

namespace First
{
    class MyClass
    {
    }
}
namespace Second
{
    class MyClass
    {
    }
}

/*--------------------------------------------------------------------------------------------------*/

 public static void Main(string[] args) //主程序
{
}

/*--------------------------------------------------------------------------------------------------*/

//變數(Variable),儲存數據的名稱

int userAge; //宣告整數

byte userAge; //宣告位元組

float pi = 3.142f; //宣告32位元浮點值

double pi = 3.142; //宣告64位元的浮點值

decimal pi = 3.142m; //宣告較高精準度的浮點

char c = 'A'; 宣告字元

bool b = true; //宣告布林值 true 或者 false

/*--------------------------------------------------------------------------------------------------*/

//Camel Casing
string thisIsAVariableName; // 駝峰式大小寫

//underscores to separate words
string this_is_a_variable_name; //將不同單字用下底線隔開

/*--------------------------------------------------------------------------------------------------*/

//初始化變數

byte = userAge = 20;

int numberOfEmployees = 510;

double numberOfHours = 5120;

float hourlyRate = 60.0f;

decimal income = 25399.65m;

char grade = '#';

bool isLoggedIn = true;

byte level = 2, userExperience = 5;

byte year;

year = 20;

/*--------------------------------------------------------------------------------------------------*/

int x = 5; //一個等於是將等號右邊的值複製給等號左邊

int y = 10;

x = y; //將 y 的值複製到 x

Console.WriteLine(x); //顯示 10

/*--------------------------------------------------------------------------------------------------*/

//基本的運算符號

int x = 7, y = 2;

Console.WriteLine( x + y ); // 9

Console.WriteLine( x - y ); // 5

Console.WriteLine( x * y ); // 14

Console.WriteLine( x / y ); // 3

Console.WriteLine( x % y ); // 1

double x = 7;

int y = 2;

Console.WriteLine( x / y ); // 3.5

/*--------------------------------------------------------------------------------------------------*/

int x = 10;

x = x + 2; // 12

x += 2;

x -= 2;

x++; //先賦值在運算

++x; //先運算在賦值

/*--------------------------------------------------------------------------------------------------*/

//類型的轉換

int x = (int)20.9;

float num1 = (float)20.9;

decimal num2 = (decimal)20.9;

/*--------------------------------------------------------------------------------------------------*/

//數組(Arrary)

int [] userAge = {21, 22, 23, 24, 25};

int [] userAge2;

userAge2 = new[] {21, 22, 23, 24, 25};

int [] userAge3 = new int[5]; // {0, 0, 0, 0, 0}

//index
userAge3[0] = 31; // {31, 0, 0, 0, 0}

userAge3[2] = userAge3[2] + 20; // {31, 0, 20, 0, 0}

/*--------------------------------------------------------------------------------------------------*/

int [] userAge = {22, 21, 23, 18, 25};

Console.WriteLine(userAge.Length); //取得數組內有多少筆資料

Array.Sort(userAge); //自動排序數組 {18, 21, 22, 23, 25}

//IndexOf
int [] numbers = {10, 30, 44, 21, 51, 21, 61, 24, 14};
int ans = Array.IndexOf(numbers, 21);
// 3, 尋找是否有此筆資料, 並返回Index, 如果找不到為-1

/*--------------------------------------------------------------------------------------------------*/

//字串

string message = "Hello World";

string message2 = "Hello World, " + " my name is Kent";

int ans = message.Length; //取得字串裡面有多少字元

Console.WriteLine(message.Substring(2)); // "llo World"

Console.WriteLine(message.Substring(2, 5)); // "llo W"
// Substring(2, 5) 起始位置, 字元的長度

/*--------------------------------------------------------------------------------------------------*/

string FirstString = "This is John";

string SecondString = "Hello";

// Equals 比較字符串是否相同

FirstString.Equals("This is John"); // true

FirstString.Equals(SecondString); // false

/*--------------------------------------------------------------------------------------------------*/

//將字串分開

char [] separator = { ' , ' , ' ; ' };

string fruits = "Apple, Banana; Dureian, , Mango";

string [] substrings = fruits.Split(separator);

Console, WriteLine(substrings);

/*--------------------------------------------------------------------------------------------------*/

//列表(Lists)

List<int> userAgeList = new List<int>();

List<int> userAgeList = new List<int>{11, 21, 31, 41};

//Add, 將資料加入List的最後

userAgeList.Add(51);

userAgeList.Add(61);

//Insert, 將資料加入指定的Index

userAgeList.Insert(2, 51);

//Remove, 將第一次找到的指定資料移除

userAgeList.Remove(51);

//RemoveAt, 將指定的Index移除

userAgeList.Remove(2);

//Contains, 檢查資料是否在List裡，並回傳布林值

userAgeList.Contains(51);

//Clear, 將List裡的資料全部清除

userAgeList.Clear();

/*--------------------------------------------------------------------------------------------------*/

// value type
int myNumber = 5;

//reference
string message = "Hello";