asp.net ajax实现无刷新验证码

时间:2021-10-16 05:31:23

1、首先是在后台验证码的aspx文件的Page_Load中的事件代码: 

复制代码代码如下:


using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
using System.Drawing; 
namespace 学生在线考试系统 

public partial class AjaxAutoCode : System.Web.UI.Page 

//验证数字 
public string authcode = string.Empty; 
protected void Page_Load(object sender, EventArgs e) 

#region 第一种产生验证码的方法 
Random random = new Random(); 
authcode = random.Next(1111, 9999).ToString(); 
//构造图片 
Bitmap image = new Bitmap(authcode.Length * 12, 25); 
//创建画布 
Graphics g = Graphics.FromImage(image); 
try 

g.Clear(Color.White); 
for (int 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); 
//链接两点的线条 
g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2); 

Font font = new Font("Arial", 12, FontStyle.Bold | FontStyle.Italic); 
System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush( 
new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkBlue, 1.2f, true); 
g.DrawString(authcode, font, brush, 2, 2); 
//画图片的前景噪点 
for (int i = 0; i < 100; i++) 

int x = random.Next(image.Width); 
int y = random.Next(image.Height); 
image.SetPixel(x, y, Color.FromArgb(random.Next())); 

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); 
ms.WriteTo(this.Response.OutputStream); 
ms.Close(); 
this.Response.ContentType = "image/gif"; 

finally 

image.Dispose(); 
g.Dispose(); 

#endregion 



2、其次在显示验证码的页面定义一个JS函数 

复制代码代码如下:


function fGetCode() 

document.getElementById("getcode").src="Default2.aspx?"+Math.random(); 


3.再编辑前台页面aspx,下面是前台页面的代码片段 

复制代码代码如下:


<label>验证码</label> 
<asp:TextBox ID="txt_checkCode" runat="server" Width="178px"></asp:TextBox> 
<img src="Default2.aspx" alt="看不清楚?" id="getcode"/> <a href="javascript:fGetCode()">更换验证码</a>