---
# System prepended metadata

title: C#

---

# C#


```
//int double decimal跟Log

int a = 50;
int b = a++;
int c = a/b;
c = c%b;
Console.WriteLine($"C={c}");
Console.WriteLine($"max={int.MaxValue},min={int.MinValue}");
int max = int.MaxValue;
a = max;
Console.WriteLine($"a={a}");
double D = 29;
double F = D++;
double G = D / F;
Console.WriteLine(G);
double Z = 1.0/3.0;
Console.WriteLine(Z);
decimal O = 1.3m;
decimal P = O++;
Console.WriteLine(O/P);
double PI = Math.PI;
double Ans = 2.50*2.50*PI;
Console.WriteLine(Ans);
```

```
 using System;
using System.Threading;


namespace 練習
{
    class Program
    {
        static void Main()
        {
         
            {
                一維陣列();
            }
        }

        static void While迴圈()
        //如果變數≠0就減到0為止    
        {
            int 倒數 = 10;
            {
                while (倒數 != 0)
                {
                    Console.WriteLine($"現在是{倒數}");
                    倒數--;
                    Thread.Sleep(1000);
                }
            }
        }
        static void Do迴圈()
        // 執行勾勾true如果勾勾是false
        {
            bool 勾勾 = false;
            do 
            {
                勾勾 = true;
                Console.WriteLine(勾勾);
                    }
            while (勾勾 == false);
            
        }
        static void For迴圈()
        //變數、條件、動作可以寫在一起(但好像動作只能寫一行剩下的還是要寫到下面去)
        {

            for (int 居然可以寫在裡面 = 0; 居然可以寫在裡面 < 10; Console.WriteLine(居然可以寫在裡面) )
            {
                居然可以寫在裡面++;
            }
        
        }
        static void 綜合()
        //分支與迴圈 
        {
            int 被除數 = 1;
            int 除數 = 3;
            int 總和 = 0;
       while (被除數 <= 20)
            {
                if (被除數 % 除數 == 0)
                {
                    總和 = 總和 + 被除數;
                    Console.WriteLine($"現在到{被除數}，可被{除數}整除，加進總和中，目前總和為{總和}");
                    被除數 ++;
                    
                }
                else if (被除數%除數 != 0)
                {
                    Console.WriteLine($"現在到{被除數}，無法被{除數}整除，不加進總和，目前總和為{總和}");
                    被除數++;
                }
            }
       //這個比較短(只是沒有直播)
            /*int sum = 0;
            for (int number = 1; number < 21; number++)
            {
                if (number % 3 == 0)
                {
                    sum = sum + number;
                }
            }*/
        }
        static void 一維陣列()
        {
            int[] a = new int[10];
            for (int b = 0; b < a.Length; b++)
            {
                a[b] = b + b;
                Console.WriteLine($"{b}相加為{a[b]}");
               a[b] = b * b;
                Console.WriteLine($"{b}相乘為{a[b]}");
            }
        }
        }

}

```

```
        static void 簡單互動應用()
        {
            {
                Console.WriteLine("say 'dododo' plz");
                string Ans = Console.ReadLine();
                switch (Ans)
                {
                    case "dododo":
                        Console.WriteLine("Nice :D");
                        break;
                    default :
                        Console.WriteLine("X");
                        Console.WriteLine("接下來該怎麼做?");
                        Console.WriteLine("輸入1 重來");
                        Console.WriteLine("輸入2 結束");
                        String Event = Console.ReadLine();
                        switch (Event)
                        {
                            case "1":
                                簡單互動應用();
                                break;
                            case "2":
                                Console.WriteLine("bye~");
                                return;
                        }
                        break;
                }
            }
         }
```

```
using OpenQA.Selenium;
using OpenQA.Selenium.Chrome;
using System;
using System.Threading;
using System.Windows.Forms;

namespace 模擬登入
{
    class Program
    {
       //

        static void Main(string[] args)
        {
            登入();
        }
        static void 登入()
        {
            Console.WriteLine("輸入帳號");
            string 帳號 = Console.ReadLine();
            Console.WriteLine("輸入密碼");
            string 密碼 = Console.ReadLine();
          
            IWebDriver driver = new ChromeDriver();
            //開網頁
            driver.Navigate().GoToUrl("https://agent.mearhh.com/login");
            //防卡頓:確定畫面跑出 資料才往下執行
            driver.Manage().Timeouts().ImplicitWait = TimeSpan.FromSeconds(10000);

            //帳號
            IWebElement inputAccount = driver.FindElement(By.Name("account"));//搜索輸入框的name
           // Thread.Sleep(500);
            inputAccount.Clear();//預防cookie先清除內容
           // Thread.Sleep(500);
            inputAccount.SendKeys(帳號);//輸入
          //  Thread.Sleep(500);

            //密碼
            IWebElement inputPassword = driver.FindElement(By.Name("password"));
            inputPassword.Clear();
          //  Thread.Sleep(500);
            inputPassword.SendKeys(密碼);
         //   Thread.Sleep(500);

            //登入
            IWebElement submitButton = driver.FindElement(By.XPath("/html/body/div[2]/form/div[3]/button"));//搜索登入鍵路徑
         //   Thread.Sleep(500);
            submitButton.Click();//鍵入
          //  driver.Navigate().GoToUrl("https://agent.mearhh.com/profile");
            SendKeys.SendWait("{F5}");
            // driver.Quit();//over
        }
    }
}
```

```
        static void Foreach迴圈()
        {
            {
                int[] BankBook = new int[5] { 1000, 2000, 3000, 4000, 5000 };
                foreach (int money in BankBook)
                {
                    Console.WriteLine("此存摺剩餘:" + money);
                }
            }

        }
```

```
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
//using System.Threading.Tasks;
using HtmlAgilityPack;
using System.Net;
using System.IO;
namespace test
{

    class Program
    {
        static void Main(string[] args)
        {
            WebClient url = new WebClient(); //指定來源網頁
            MemoryStream ms = new MemoryStream(url.DownloadData("http://www.coolpc.com.tw/evaluate.php"));//將網頁來源資料暫存到記憶體內
            HtmlDocument doc = new HtmlDocument();// 使用預設編碼讀入 HTML 
            doc.Load(ms, Encoding.Default);          
            if (doc != null)
            {
                var list_type = new List<string>();
                HtmlNodeCollection nodes = doc.DocumentNode.SelectNodes("//select[@name='n4']//optgroup");

                foreach (HtmlNode node in nodes)
                {
                    var type = node.Attributes["label"].Value;
                    list_type.Add(type);
                }

                List<string> list_name = doc.DocumentNode.SelectSingleNode("//select[@name='n4']").InnerText.Split('\n').ToList();

                //刪除不必要的非商品選項
                list_name.RemoveRange(0, 3);
                list_name.RemoveAt(list_name.Count - 1);

                var models = new List<Product>();
                int number = 0;
                for (int i = 0; i < list_name.Count; i++)
                {
                    string type = list_type[number];
                    string name = list_name[i];

                    if (name == "")
                    {
                        number++;
                    }
                    else
                    {
                        models.Add(new Product()
                        {
                            type = type,
                            name = name
                        });

                        Console.WriteLine("類型：{0} ,", type);
                        Console.WriteLine("名稱：{0}", name);
                    }
                }

                Console.ReadLine();
            }

        }
    }

    class Product
    {
        public string type { get; set; }

        public string name { get; set; }
    }
}

```
```
//unchecked、checked
 try
{
    unchecked //un不檢查 但會倒扣 check會直接回傳溢位
    {
        int A = int.MinValue;
        int B = 1;
        int C = A - B;
        Console.WriteLine($"{A},{B},{C}");
    }
}
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }
Console.ReadLine();
```
```

```
```

```
```