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Controller
using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; using Utility; using Jellal**; namespace sjlwebsite.Controllers { public class CommonController : Controller { #region 验证码 [OutputCache(Duration = 0)] public ActionResult VCode() { string code = ValidateCode.CreateRandomCode(4); Session["vcode"] = code; ValidateCode.CreateImage(code); return View(); } public string GetCode() { return Session["vcode"].ToStr(); } #endregion } }
Verification code class
using System; using System.Collections; using System.ComponentModel; using System.Data; using System.Drawing; using System.Web; using System.Web.SessionState; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.HtmlControls; namespace Utility { /// <summary> /// 完美随机验证码 0.10 /// Verion:0.10 /// Description:随机生成设定验证码,并随机旋转一定角度,字体颜色不同 /// </summary> public class ValidateCode { /// <summary> /// 生成随机码 /// </summary> /// <param name="length">随机码个数www.52mvc.com</param> /// <returns></returns> public static string CreateRandomCode(int length) { int rand; char code; string randomcode = String.Empty; //生成一定长度的验证码 System.Random random = new Random(); for (int i = 0; i < length; i++) { rand = random.Next(); if (rand % 3 == 0) { code = (char)('A' + (char)(rand % 26)); } else { code = (char)('0' + (char)(rand % 10)); } randomcode += code.ToString(); } return randomcode; } /// <summary> /// 创建随机码图片 /// </summary> /// <param name="randomcode">随机码</param> public static void CreateImage(string randomcode) { int randAngle = 45; //随机转动角度 int mapwidth = (int)(randomcode.Length * 23); Bitmap map = new Bitmap(mapwidth, 28);//创建图片背景 Graphics graph = Graphics.FromImage(map); graph.Clear(Color.AliceBlue);//清除画面,填充背景 graph.DrawRectangle(new Pen(Color.Black, 0), 0, 0, map.Width - 1, map.Height - 1);//画一个边框 //graph.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;//模式 Random rand = new Random(); //背景噪点生成 www.jb51.net Pen blackPen = new Pen(Color.LightGray, 0); for (int i = 0; i < 50; i++) { int x = rand.Next(0, map.Width); int y = rand.Next(0, map.Height); graph.DrawRectangle(blackPen, x, y, 1, 1); } //验证码旋转,防止机器识别 char[] chars = randomcode.ToCharArray();//拆散字符串成单字符数组 //文字距中 StringFormat format = new StringFormat(StringFormatFlags.NoClip); format.Alignment = StringAlignment.Center; format.LineAlignment = StringAlignment.Center; //定义颜色 Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple }; //定义字体 string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" }; for (int i = 0; i < chars.Length; i++) { int cindex = rand.Next(7); int findex = rand.Next(5); Font f = new System.Drawing.Font(font[findex], 13, System.Drawing.FontStyle.Bold);//字体样式(参数2为字体大小) Brush b = new System.Drawing.SolidBrush(c[cindex]); Point dot = new Point(16, 16); //graph.DrawString(dot.X.ToString(),fontstyle,new SolidBrush(Color.Black),10,150);//测试X坐标显示间距的 float angle = rand.Next(-randAngle, randAngle);//转动的度数 graph.TranslateTransform(dot.X, dot.Y);//移动光标到指定位置 graph.RotateTransform(angle); graph.DrawString(chars.ToString(), f, b, 1, 1, format); //graph.DrawString(chars.ToString(),fontstyle,new SolidBrush(Color.Blue),1,1,format); graph.RotateTransform(-angle);//转回去 graph.TranslateTransform(2, -dot.Y);//移动光标到指定位置 } //graph.DrawString(randomcode,fontstyle,new SolidBrush(Color.Blue),2,2); //标准随机码 //生成图片 System.IO.MemoryStream ms = new System.IO.MemoryStream(); map.Save(ms, System.Drawing.Imaging.ImageFormat.Gif); HttpContext.Current.Response.ClearContent(); HttpContext.Current.Response.ContentType = "image/gif"; HttpContext.Current.Response.BinaryWrite(ms.ToArray()); graph.Dispose(); map.Dispose(); } } }
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The char array stores character sequences in C language and is declared as char array_name[size]. The access element is passed through the subscript operator, and the element ends with the null terminator '\0', which represents the end point of the string. The C language provides a variety of string manipulation functions, such as strlen(), strcpy(), strcat() and strcmp().

The usage methods of symbols in C language cover arithmetic, assignment, conditions, logic, bit operators, etc. Arithmetic operators are used for basic mathematical operations, assignment operators are used for assignment and addition, subtraction, multiplication and division assignment, condition operators are used for different operations according to conditions, logical operators are used for logical operations, bit operators are used for bit-level operations, and special constants are used to represent null pointers, end-of-file markers, and non-numeric values.

In C language, special characters are processed through escape sequences, such as: \n represents line breaks. \t means tab character. Use escape sequences or character constants to represent special characters, such as char c = '\n'. Note that the backslash needs to be escaped twice. Different platforms and compilers may have different escape sequences, please consult the documentation.

The difference between multithreading and asynchronous is that multithreading executes multiple threads at the same time, while asynchronously performs operations without blocking the current thread. Multithreading is used for compute-intensive tasks, while asynchronously is used for user interaction. The advantage of multi-threading is to improve computing performance, while the advantage of asynchronous is to not block UI threads. Choosing multithreading or asynchronous depends on the nature of the task: Computation-intensive tasks use multithreading, tasks that interact with external resources and need to keep UI responsiveness use asynchronous.

In C, the char type is used in strings: 1. Store a single character; 2. Use an array to represent a string and end with a null terminator; 3. Operate through a string operation function; 4. Read or output a string from the keyboard.

In C language, char type conversion can be directly converted to another type by: casting: using casting characters. Automatic type conversion: When one type of data can accommodate another type of value, the compiler automatically converts it.

There is no built-in sum function in C language, so it needs to be written by yourself. Sum can be achieved by traversing the array and accumulating elements: Loop version: Sum is calculated using for loop and array length. Pointer version: Use pointers to point to array elements, and efficient summing is achieved through self-increment pointers. Dynamically allocate array version: Dynamically allocate arrays and manage memory yourself, ensuring that allocated memory is freed to prevent memory leaks.

In C language, the main difference between char and wchar_t is character encoding: char uses ASCII or extends ASCII, wchar_t uses Unicode; char takes up 1-2 bytes, wchar_t takes up 2-4 bytes; char is suitable for English text, wchar_t is suitable for multilingual text; char is widely supported, wchar_t depends on whether the compiler and operating system support Unicode; char is limited in character range, wchar_t has a larger character range, and special functions are used for arithmetic operations.


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