大家好，今天一起學習如何寫一個 寫一個圖形驗證碼。

Step 1. 先using 會使用到的類別

using System.Drawing;
using System.IO;

Step 1. Controller 程式碼
1-1測試的輸入頁面

 public ActionResult TEST()
 {
        
     return View();
 }

1-2 驗證的頁面

   [HttpPost]
   public ActionResult Login()
   {
       string code = Request.Form["code"].ToString();
       if (code == TempData["code"].ToString())
       {
            ViewBag.code = code;
            ViewBag.Ans = TempData["code"];
            ViewBag.Result = "驗證正確";
            return View();
        }
        else 
        {               
           ViewBag.code = code;
           ViewBag.Ans = TempData["code"];
           ViewBag.Result = "驗證錯誤";
           return View();
        }
     
       
    }

1-3 隨機生成指定長度的驗證碼字符串

  private string RandomCode(int length)
    {
        string s = "0123456789zxcvbnmasdfghjklqwertyuiop";
        StringBuilder sb = new StringBuilder();
        Random rand = new Random();
        int index;
        for (int i = 0; i < length; i++)
        {
            index = rand.Next(0, s.Length);
            sb.Append(s[index]);
        }
        return sb.ToString();
    }

1-4 產生刪除線 num 代表幾條

 private void PaintInterLine(Graphics g, int num, int width, int height)
    {
        Random r = new Random();
        int startX, startY, endX, endY;
        for (int i = 0; i < num; i++)
        {
            startX = r.Next(0, width);
            startY = r.Next(0, height);
            endX = r.Next(0, width);
            endY = r.Next(0, height);
            g.DrawLine(new Pen(Brushes.Red), startX, startY, endX, endY);
        }
    }

1-5 畫出 圖形驗證碼

 public ActionResult GetValidateCode()
    {
        byte[] data = null;
        string code = RandomCode(5);
        TempData["code"] = code;
        //定義一個畫板
        MemoryStream ms = new MemoryStream();
        using (Bitmap map = new Bitmap(100, 40))
        {
            //畫筆,在指定畫板畫板上畫圖
            //g.Dispose();
            using (Graphics g = Graphics.FromImage(map))
            {
                g.Clear(Color.White);
                g.DrawString(code, new Font("黑體", 18.0F), Brushes.Blue, new Point(10, 8));
                //繪製干擾線(數字代表幾條)
                PaintInterLine(g, 10, map.Width, map.Height);
            }
            map.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
        }
        data = ms.GetBuffer();
        return File(data, "image/jpeg");
    }

Step 2 View的部分

2-1 TEST.cshtml

@{
    ViewBag.Title = "TEST";
}

<h2>TEST</h2>

<form method="post" id="form1" action="/Home/Login">
    <div class="code">
        <input type="text" name="code" />
        <img id="code" src="/Home/GetValidateCode/" />

    </div>
    <div>
        <input type="submit" value="登錄" />
    </div>
</form>

2-2 Login.cshtml

@{
    ViewBag.Title = "Login";
}

<h2>Login</h2>

輸入的值： @ViewBag.code <br/>
答案的值： @ViewBag.Ans <br />
驗證結果 @ViewBag.Result <br />

Step 3. 成果畫面

3-1 成功

3-2 失敗

參考網址：
C#之asp.net 及MVC 生成動態驗證碼：