ASP.NET——验证码的制作
我们在登陆站点,发表博客或者提交评论的时候,常常会遇到填写验证码这一项,当时感觉挺奇妙的样子,最终在牛腩新闻公布系统里接触到了,在这里小小的总结下。
用到的东东有三个:一个aspx页面,一个图片
首先,建立一个aspx页面。
<%@ WebHandler Language="C#" Class="Picture" %> using System; using System.Web; using System.Drawing; using System.Drawing.Drawing2D; using System.Web.SessionState; public class Picture : IHttpHandler, IRequiresSessionState // 要使用session必须实现该接口,记得要导入System.Web.SessionState命名空间 { public void ProcessRequest(HttpContext context) { string checkCode = GenCode(5); // 产生5位随机字符 context.Session["Code"] = checkCode; //将字符串保存到Session中,以便须要时进行验证 System.Drawing.Bitmap image = new System.Drawing.Bitmap(70, 22); Graphics g = Graphics.FromImage(image); try { //生成随机生成器 Random random = new Random(); //清空图片背景色 g.Clear(Color.White); // 绘图片的背景噪音线 int i; for (i = 0; i < 25; i++) { int x1 = random.Next(image.Width); int x2 = random.Next(image.Width); int y1 = random.Next(image.Height); int y2 = random.Next(image.Height); g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2); } Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold)); System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2F, true); g.DrawString(checkCode, font, brush, 2, 2); //绘图片的前景噪音点 g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1); System.IO.MemoryStream ms = new System.IO.MemoryStream(); image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif); context.Response.ClearContent(); context.Response.ContentType = "image/Gif"; context.Response.BinaryWrite(ms.ToArray()); } finally { g.Dispose(); image.Dispose(); } } /// <summary> /// 产生随机字符串 /// </summary> /// <param name="num">随机出几个字符</param> /// <returns>随机出的字符串</returns> private string GenCode(int num) { string str = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"; char[] chastr = str.ToCharArray(); string code = ""; Random rd = new Random(); int i; for (i = 0; i < num; i++) { //code += source[rd.Next(0, source.Length)]; code += str.Substring(rd.Next(0, str.Length), 1); } return code; } public bool IsReusable { get { return false; } } }其次,在用到验证码的界面加入一个img控件,而且src属性指向.ashx文件。
<img src="handler/WaterMark.ashx" id="vimg" alt="" onclick="changeCode()"/>
然后,推断提交的验证码是否正确。
//推断验证码是否输入正确 string code = txtCode.Text.Trim().ToUpper();//将输入的字母都转化成大写然后作比較 string rightCode = Session["Code"].ToString(); if(code!=rightCode ) { Page.ClientScript.RegisterStartupScript(Page.GetType(), "message", "<script language='javascript' defer>alert('验证码输入错误!');</script>");//提示错误保证后面背景不变白 return; }
最后,使用JavaScrip来刷新验证码。由于代码比較少,所以能够嵌套在代码中。
<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server"> <script language="javascript" type="text/javascript"> function changeCode() { var imgNode = document.getElementById("vimg"); imgNode.src = "handler/WaterMark.ashx?t=" + (new Date()).valueOf(); // 这里加个时间的參数是为了防止浏览器缓存的问题 } </script> </asp:Content>