【6月日新计划01】C#入门介绍-簡單運算,邏輯判斷

C# 实际上是微软的旗舰语言。它是相当通用的——你可以用它来编写 各种程序，从传统的控制台和桌面应用，通过网站和服务到移动开发， 无论是商业还是娱乐。

C# 开发工具： Visual Studio。

1. Hello C#

using System; 
namespace My_first_program 
{ 
    class Program 
    { 
        static void Main(string[] args) 
        { 
            // Output of text to the user 
            Console.WriteLine("I am starting to program in C#.");
            // Waiting for Enter 
            Console.ReadLine(); 
        }
    } 
}

特殊字符，需要转义

using System; 
namespace My_first_program 
{ 
    class Program 
    { 
        static void Main(string[] args) 
        { 
            // Multiline output 
            Console.WriteLine("First line\r\nSecond line");
            Console.ReadLine(); 
        }
    } 
}

多行文本，在文本的左引号前加上(@)符号，注意(@)符号也关闭转义序列

2. Object

2.1 DateTime

显示当前日期和时间

static void Main(string[] args) 
{ 
    // Current date and time (using single statement) 
    DateTime now = DateTime.Now; 
    // Picking up individual components 
    int day = now.Day; 
    int month = now.Month; 
    int year = now.Year; 
    int hours = now.Hour; 
    int minutes = now.Minute; 
    int seconds = now.Second; 
    DateTime justDateWithoutTime = now.Date; 
    // Output Console.WriteLine("Day: " + day); 
    Console.WriteLine("Month: " + month); 
    Console.WriteLine("Year: " + year); 
    Console.WriteLine("Hours: " + hours); 
    Console.WriteLine("Minutes: " + minutes);
    Console.WriteLine("Seconds: " + seconds); 
    Console.WriteLine("Our output: " + year + ", " + month + "/" + day + " " + hours + " hours " + minutes + " minutes"); 
    
    // Waiting for Enter 
    Console.ReadLine(); }

仅显示日期

static void Main(string[] args) 
{ 
    // Variable of DateTime type, at first empty 
    DateTime today; 
    // Storing of today's date (without time component) 
    today = DateTime.Today; 
    Console.WriteLine("Today is " + today); 
    
    DateTime tomorrow = today.AddDays(1);
    Console.WriteLine("Tomorrow is " + tomorrow);   
    // Waiting for Enter 
    Console.ReadLine(); }

2.2 Random

static void Main(string[] args) 
{ 
    // Creating random number generator object 
    Random randomNumbers = new Random(); 
    // Repeatedly throwing a die 
    int number1 = randomNumbers.Next(1, 6 + 1); 
    int number2 = randomNumbers.Next(1, 6 + 1); 
    int number3 = randomNumbers.Next(1, 6 + 1); 
    // Output 
    Console.WriteLine("Thrown numbers: " + number1 + ", " + number2 + ", " + number3); 
    
    // Waiting for Enter 
    Console.ReadLine(); }

2.3 Console

static void Main(string[] args) 
{ 
    // Hinting user what we want from her 
    Console.Write("Enter a sentence (and press Enter):"); 
    // Reading line of text 
    string input = Console.ReadLine(); 
    // Repeating to the output 
    Console.WriteLine("You have entered: " + input);
    // Waiting for Enter 
    Console.ReadLine(); 
}

2.4 Basic Operation

数字运算

static void Main(string[] args) 
{ 
    // Inputs 
    Console.Write("Enter first number: "); 
    string input1 = Console.ReadLine(); 
    double number1 = Convert.ToDouble(input1); 
    Console.Write("Enter second number: "); 
    string input2 = Console.ReadLine(); 
    double number2 = Convert.ToDouble(input2); 
    
    // Calculations 
    double sum = number1 + number2; 
    double difference = number1 - number2; 
    double product = number1 * number2; 
    double quotient = number1 / number2; 
    
    // Output 
    Console.WriteLine("Sum is " + sum); 
    Console.WriteLine("Difference is " + difference); 
    Console.WriteLine("Product is " + product); 
    Console.WriteLine("Quotient is " + quotient); 
    
    // Waiting for Enter 
    Console.ReadLine(); 
}

日期运算

static void Main(string[] args) 
{ 
    // Input 
    Console.Write("Enter your date of birth: "); 
    string input = Console.ReadLine(); 
    DateTime dateOfBirth = Convert.ToDateTime(input); 
    
    // Today 
    DateTime today = DateTime.Today; 
    // Date difference 
    TimeSpan difference = today - dateOfBirth; 
    int numberOfDays = difference.Days; 
    
    // Output 
    Console.WriteLine(); 
    Console.WriteLine("Today is: " + today.ToShortDateString Console.WriteLine("The world likes you for this number of days: " 
    
    // Waiting for Enter Console.ReadLine(); }

时区和UTC

static void Main(string[] args) 
{ 
    // Current time serves as input 
    DateTime now = DateTime.Now; 
    DateTime utcNow = DateTime.UtcNow;
    DateTimeOffset completeInstant = DateTimeOffset.Now; 
    DateTimeOffset utcCompleteInstant = DateTimeOffset.UtcNow; 
    // Outputs 
    Console.WriteLine("Now: " + now); 
    Console.WriteLine("UTC now: " + utcNow); 
    Console.WriteLine("Now (including time zone): " + completeInstant   
    Console.WriteLine("Time zone (offset against UTC): " + utcCompleteInstant
    // Waiting for Enter 
    Console.ReadLine(); }

3. Conditions

3.1 if

if...else....

if (user1ok || user2ok) { 
    Console.WriteLine("Thanks for your books!"); 
} else { 
    Console.WriteLine("Could not log you in."); 
}

3.2 logic

&& ||

if (user1ok || user2ok) { 
    Console.WriteLine("Thanks for your books!"); 
} else { 
    Console.WriteLine("Could not log you in."); 
}

4. Loop

static void Main(string[] args) 
{ 
    // Output 
    for (int count = 0; count < 10; count++) { 
        Console.WriteLine("I will start learning tomorrow." 
    } 
    
    // Waiting for Enter 
    Console.ReadLine(); 
}

4.1 反复投骰子

static void Main(string[] args) 
{ 
    // Random number generator 
    Random randomNumbers = new Random(); 
    // Output，next方法1是下限，6是上限 
    for (int count = 0; count < 20; count++) { 
        int thrown = randomNumbers.Next(1, 6 + 1); 
        Console.Write(thrown.ToString() + " "); 
    } 
    
    // Waiting for Enter 
    Console.ReadLine(); 
}

5. 打印對象屬性

    public void PropertyList(this object obj)
    {
          var props = obj.GetType().GetProperties();
          var sb = new StringBuilder();
          foreach (var p in props)
          {
            sb.AppendLine(p.Name + ": " + p.GetValue(obj, null));
          }
          System.Diagnostics.Trace.WriteLine(sb.ToString()); 
    }