当前文件路径：AllInOneValidCode/Default.aspx 
1
<%...@ import namespace="System"%>
2<%...@ import namespace="System.io"%>
3<%...@ import namespace="System.Drawing"%>
4<%...@ import namespace="System.Drawing.Imaging"%>
5<script language="vb" runat="server">...
6
Sub Page_Load(Sender as object,e as eventargs)
7'RndNum是一个自定义函数
8dim VNum as string=RndNum(4)
9Session("VNum")=VNum
10ValidateCode(VNum)
11End Sub
12'生成图象验证码函数
13Sub ValidateCode(VNum)
14Dim Img as System.Drawing.Bitmap
15Dim g as Graphics
16Dim ms as MemoryStream
17 Dim gheight As Integer = Int(Len(VNum) * 16)
18'gheight为图片宽度,根据字符长度自动更改图片宽度
19img=new BitMap(Gheight,20)
20g=Graphics.FromImage(img)
21g.DrawString(VNum,(New Font("Arial",10)),(New SolidBrush(color.blue)),3,3)'在矩形内绘制字串（字串，字体，画笔颜色，左上x.左上y）
22ms=New MemoryStream()
23img.Save(ms,ImageFormat.Png)
24Response.ClearContent() '需要输出图象信息 要修改HTTP头
25Response.ContentType="image/Png"
26Response.BinaryWrite(ms.ToArray())
27g.Dispose()
28img.Dispose()
29Response.End()
30End Sub
31'--------------------------------------------
32'函数名称:RndNum
33'函数参数:VcodeNum--设定返回随机字符串的位数
34'函数功能:产生数字和字符混合的随机字符串
35Function RndNum(VcodeNum)
36 Dim Vchar As String = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z,呵,呵,弹,簧,秤,嬉,戏"
37dim VcArray() as string=split(Vchar,",") '将字符串生成数组
38dim VNum as string=""
39dim i as byte
40For i=1 to VcodeNum
41Randomize
42 VNum = VNum & VcArray(Int(42 * Rnd())) '数组一般从0开始读取，所以这里为35*Rnd
43Next
44Return VNum
45End Function
46</script>
47<html xmlns="http://www.w3.org/1999/xhtml">
48<head>
49<title></title>
50</head>
51<body>
52
53</body>
54
</html>
打包下载该项目完整源码：字母\数字\汉字混合的验证码源码
