C#制作登录验证码

后台代码：

public ActionResult VerificationCode()
        {
            try
            {
                int _verificationLength = 4;//密码长度
                int _width = 100, _height = 50;
                SizeF _verificationTextSize;
                Random r = new Random();
                Bitmap _bitmap = new Bitmap(Server.MapPath("~/Common/Texture" + (int)r.Next(0, 3) + ".jpg"), true);//此处用的图片
                TextureBrush _brush = new TextureBrush(_bitmap);
                //获取验证码
                string _verificationText = ValidateCode.VerificationText(_verificationLength);
                //存储验证码
                Session["VerificationCode"] = _verificationText.ToUpper();
                Font _font = new Font("Arial", 14, FontStyle.Bold);
                Bitmap _image = new Bitmap(_width, _height);
                Graphics _g = Graphics.FromImage(_image);
                //清空背景色
                _g.Clear(Color.White);
                //绘制验证码
                _verificationTextSize = _g.MeasureString(_verificationText, _font);
                _g.DrawString(_verificationText, _font, _brush, (_width - _verificationTextSize.Width) / 2, (_height - _verificationTextSize.Height) / 2);
                _image.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
                HttpContext.Response.Write(_image);
            }
            catch (Exception)
            {

            }
            return null;
        }

前端代码：

<td>
   <img src="" class="add-on" id="vcode" title="点击更换验证码" style="float:left;clear:both;line-height:12px;border-radius:4px;" />
   <a class="span1 pull-left" style="margin-top:4px;" onclick="getValidateCode();">点击图片可更换验证码</a>
 </td>

JS代码：

function getValidateCode() {
            //获取验证码
            $("img#vcode").attr("src", "/manager/Login/VerificationCode?" + new Date());
            $("img#vcode").click(function () {
                $(this).attr("src", "/manager/Login/VerificationCode?" + new Date());
                $("#vcode").val("");//清空验证码输入框内容
            });
        }