Ajax校验验证码（可以设置为数字、字母、中文汉字等，背景图有干扰线）

/// <summary>
/// VCode 的摘要说明
/// </summary>
public class VCode : IHttpHandler,System.Web.SessionState.IRequiresSessionState
{
public void ProcessRequest(HttpContext context)
{
//System.Threading.Thread.Sleep(5000);
context.Response.ContentType = "image/jpeg";
string code = GetRndNumStr();
//string code = GetRndNum();
//string code = GetRndStr();
//string code = GetRndCh();
context.Session["VCode"] = code;
using (Bitmap img = CreateImages(code, "ch"))
{
img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
}
}
// 数字+字母随机
private string GetRndNumStr()
{
string Vchar = "A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,0,1,2,3,4,5,6,7,8,9";
string[] VcArray = Vchar.Split(',');
string checkCode = string.Empty;
Random rand = new Random();
for (int i = 0; i < 4; i++)
{
int t = rand.Next(VcArray.Length);
checkCode += VcArray[t];
}
return checkCode;
}
// 数字随机数
private string GetRndNum()
{
string code = string.Empty;
Random random = new Random();
for (int i = 0; i < 4; i++)
{
code += random.Next(9);
}
return code;
}
// 英文随机
private string GetRndStr()
{
string Vchar = "A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";
string[] VcArray = Vchar.Split(',');
string checkCode = string.Empty;
Random rand = new Random();
for (int i = 0; i < 4; i++)
{
int t = rand.Next(VcArray.Length);
checkCode += VcArray[t];
}
return checkCode;
}
// 中文随机
private string GetRndCh()
{
System.Text.Encoding gb = System.Text.Encoding.Default;//获取GB2312编码页（表）
object[] bytes = CreateRegionCode(4);//生4个随机中文汉字编码
string[] str = new string[4];
System.Text.StringBuilder sb = new System.Text.StringBuilder();
for (int i = 0; i < 4; i++)
{
//根据汉字编码的字节数组解码出中文汉字
str[i] = gb.GetString((byte[])Convert.ChangeType(bytes[i], typeof(byte[])));
sb.Append(str[i].ToString());
}
return sb.ToString();
}
// 产生随机中文字符
private static object[] CreateRegionCode(int strlength)
{
//定义一个字符串数组储存汉字编码的组成元素
string[] rBase = new String[16] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
Random rnd = new Random();
object[] bytes = new object[strlength];

for (int i = 0; i < strlength; i++)
{
//区位码第1位
int r1 = rnd.Next(11, 14);
string str_r1 = rBase[r1].Trim();
//区位码第2位
rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i);
int r2;
if (r1 == 13)
{
r2 = rnd.Next(0, 7);
}
else
{
r2 = rnd.Next(0, 16);
}
string str_r2 = rBase[r2].Trim();

//区位码第3位
rnd = new Random(r2 * unchecked((int)DateTime.Now.Ticks) + i);//更换随机种子
int r3 = rnd.Next(10, 16);
string str_r3 = rBase[r3].Trim();

//区位码第4位
rnd = new Random(r3 * unchecked((int)DateTime.Now.Ticks) + i);
int r4;
if (r3 == 10)
{
r4 = rnd.Next(1, 16);
}
else if (r3 == 15)
{
r4 = rnd.Next(0, 15);
}
else
{
r4 = rnd.Next(0, 16);
}
string str_r4 = rBase[r4].Trim();
//定义两个字节变量存储产生的随机汉字区位码
byte byte1 = Convert.ToByte(str_r1 + str_r2, 16);
byte byte2 = Convert.ToByte(str_r3 + str_r4, 16);

//将两个字节变量存储在字节数组中
byte[] str_r = new byte[] { byte1, byte2 };

//将产生的一个汉字的字节数组放入object数组中
bytes.SetValue(str_r, i);
}
return bytes;
}
// 画图片的背景图+干扰线
private Bitmap CreateImages(string checkCode, string type)
{
int step = 0;
if (type == "ch")
{
step = 5;//中文字符，边界值做大
}
int iwidth = (int)(checkCode.Length * (13 + step));
System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 22);
Graphics g = Graphics.FromImage(image);
g.Clear(Color.White);//清除背景色
Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };//定义随机颜色
string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
Random rand = new Random();

for (int i = 0; i < 50; i++)
{
int x1 = rand.Next(image.Width);
int x2 = rand.Next(image.Width);
int y1 = rand.Next(image.Height);
int y2 = rand.Next(image.Height);
g.DrawLine(new Pen(Color.LightGray, 1), x1, y1, x2, y2);//根据坐标画线
}

for (int i = 0; i < checkCode.Length; i++)
{
int cindex = rand.Next(7);
int findex = rand.Next(5);

Font f = new System.Drawing.Font(font[findex], 10, System.Drawing.FontStyle.Bold);
Brush b = new System.Drawing.SolidBrush(c[cindex]);
int ii = 4;
if ((i + 1) % 2 == 0)
{
ii = 2;
}
g.DrawString(checkCode.Substring(i, 1), f, b, 3 + (i * (12 + step)), ii);

}
g.DrawRectangle(new Pen(Color.Black, 0), 0, 0, image.Width - 1, image.Height - 1);
System.IO.MemoryStream ms = new System.IO.MemoryStream();
return image;
}

public bool IsReusable
{
get
{
return false;
}
}
}

验证码:
<input id="txtVcode" type="text" />
<img alt="" id="imgCode" src="/js/vcode/VCode.ashx" />
<a id="aCode" href="javascript:void(0)">看不清，换一张</a>
<div id="txtVcodeTip"></div>

function getVCode() {
$("#imgCode").attr("src", "/js/vcode/VCode.ashx?r=" + new Date());
}
$(function () {
//验证码
var imgCode = $("#imgCode");
imgCode.attr("alt", "点击获取验证码");
imgCode.attr("title", "点击更换验证码");
imgCode.css("cursor", "pointer");
imgCode.click(function () {//点击验证码本身切换验证码
getVCode();
});
//点击文字超链接更换验证码
var aCode = $("#aCode");
aCode.click(function () {
getVCode();
});
//验证码提示消息
var vcodeMsg = $("#txtVcodeTip");
vcodeMsg.css("color", "Red");
var vcode = $("#txtVcode");
vcode.blur(function () {
if ($.trim(vcode.val()) == '') {
vcodeMsg.text("验证码不能为空");
return false;
} else {
$.post("/js/vcode/CheckVCode.ashx", { "vcode": $.trim(vcode.val()) }, function (data) {
vcodeMsg.text(data);
});
}
}).focus(function () {
vcodeMsg.text("");
});
});

public class CheckVCode : IHttpHandler, System.Web.SessionState.IRequiresSessionState
{

public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "text/plain";
string vcode = context.Request["vcode"];
context.Response.Write(CheckCode(vcode));
}

public static string CheckCode(string vcode)
{
if (HttpContext.Current.Session["VCode"] != null)
{
string sysCode = HttpContext.Current.Session["VCode"].ToString();
//使用  Compare  方法，这个方法可以做大小写忽略的比较，并且不会创建新字符串
if (String.Compare(vcode, sysCode, true) == 0)
{
return "ok";
}
else
{
return "验证码输入错误,重新输入";
}
}
else
{
return "验证码过期，请更换验证码";
}
}

public bool IsReusable
{
get
{
return false;
}
}
}