C# 一般处理程序ashx用于验证码

1、用VS2019建立一个web应用程序，选mvc模板

2、选中项目邮件新建文件夹Webservice，然后添加一般处理程序Verify.ashx然后右键打开改写如下

 public class VerifyCode : IHttpHandler, IRequiresSessionState
    {

        public bool IsReusable { get { return false; } }
        private const int width = 90;
        private const int height = 30;
        public void ProcessRequest(HttpContext context)
        {
            context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
            context.Response.ClearContent();
            context.Response.ContentType = "image/Png";
            context.Response.BinaryWrite(CreateImg(ExfSoft.Common.SecurityUtil.CreateNew(4, true)));
            context.Response.End();
        }

        private byte[] CreateImg(string VerifyCode)
        {
            //这个宽高可以根据需要确定 
            System.Drawing.Bitmap image = new Bitmap(width, height);
            //创建图形
            Graphics g = Graphics.FromImage(image);
            //创建RectangleF结构指定一个区域
            RectangleF rectangle = new RectangleF(0, 0, image.Width, image.Height);
            g.FillRectangle(new SolidBrush(Color.FromArgb(255, 255, 255)), rectangle);

            //背景噪音线
            System.Random random = new Random();
            for (int i = 0; i < 15; i++)
            {
                int x1 = random.Next(width);
                int x2 = random.Next(width);
                int y1 = random.Next(height);
                int y2 = random.Next(height);
                g.DrawLine(new Pen(Color.FromArgb(random.Next())), x1, y1, x2, y2);
            }
            Font font = new Font("Arial", 14, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
            LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, width, height), Color.Blue, Color.DarkRed, 1.2f, true);

            var chars = new List<Char>();
            foreach (char s in VerifyCode)
            {
                chars.Add(s);
            }

            g.DrawString(String.Join(" ", chars.ToArray()), font, brush, 10, 5);

            //画图片的前景噪音点
            for (int i = 0; i < 50; i++)
            {
                int x = random.Next(width);
                int y = random.Next(height);
                image.SetPixel(x, y, Color.FromArgb(random.Next()));
            }
            //画图片的边框线
            g.DrawRectangle(new Pen(Color.FromArgb(255, 153, 193, 226)), 0, 0, image.Width - 1, image.Height - 1);

            MemoryStream ms = new MemoryStream();
            //选择透明格式
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
            //原本是准备输出html流，现在输出图信数据，所以要修改http头
            return ms.ToArray();
        }
    }

3、任意找一个页面如Index.cshtml，添加图片控件和Jquery代码

<img id="verifycode_img" src="/webservice/verifycode.ashx" onclick="" style="vertical-align: middle; margin-left: 10px;" />

<script>
    $(function () {
        $("#verifycode_img").click(function () {
            $(this).attr('src', '/WebService/VerifyCode.ashx?t=' + new Date())
        })
    })
</script>

4、效果，点击图片验证码将会做相应变化

 5、配合input框提交到后台Action里面通过，ExfSoft.Common.SecurityUtil.IsValid("验证码字符串")方法，即可以实现登录验证码功能。