本篇文章给大家分享的是有关VB.NET中怎么生成验证码，小编觉得挺实用的，因此分享给大家学习，希望大家阅读完这篇文章后可以有所收获，话不多说，跟着小编一起来看看吧。
VB.NET生成验证码前台代码为:
< asp:image id="Image2"
runat="server" ImageUrl=
"ValidateCode.aspx">
ValidateCode.aspx文件的代码为：
Private Sub Page_Load
(ByVal sender As System.Object,
ByVal e As System.EventArgs)
Handles MyBase.Load
list()
End Sub
Function list()
在此处放置初始化页的用户代码，rndnum是一个自定义函数
计算
安全
数据库
网络和加速
企业服务
Dim vnum As String = rndnum(4) Session("vnum") = vnum validatecode(vnum) End Function VB.NET生成验证码生成图象验证码函数
Sub validatecode(ByVal vnum) Dim img As System.drawing.Bitmap Dim g As Graphics Dim r As Random = New Random Dim gheight As IntInteger = Int(Len(vnum) * 13) gheight为图片宽度,根据字符长度自动更改图片宽度
img = New Bitmap(gheight, 20) g = Graphics.FromImage(img) 'g.DrawString(vnum, New System.Drawing.Font("Arial", 10), New System.Drawing.SolidBrush(Color.Blue), 3, 3) 新增，修改、画图片的背景噪音线
'For i As Integer = 0 To 25 For i As Integer = 0 To 10 Dim x1 As Integer x1 = r.Next(img.Width) Dim x2 As Integer = r.Next(img.Width) Dim y1 As Integer = r.Next(img.Height) Dim y2 As Integer = r.Next(img.Height) g.DrawLine(New Pen(Color.Silver), x1, y1, x2, y2) Next i Dim font As font font = New System.Drawing.Font("Arial", 12) Dim brush As System.Drawing.Drawing2D.LinearGradientBrush brush = New System.Drawing.Drawing2D.LinearGradientBrush(New Rectangle(0, 0, img.Width, img.Height), Color.Blue, Color.Blue, 1.2F, True) g.DrawString(vnum, font, brush, 2, 2) VB.NET生成验证码中画图片的前景噪音点
'For ii As Integer = 0 To 100 ' Dim x As Integer = r.Next(img.Width) ' Dim y As Integer = r.Next(img.Height) ' img.SetPixel(x, y, Color.FromArgb(r.Next())) 'Next 画图片的边框线
g.DrawRectangle(New Pen(Color.Silver), 0, 0, img.Width - 1, img.Height - 1) 在矩形内绘制字串（字串，字体，画笔颜色，左上x.左上y）
Dim ms1 As System.IO.MemoryStream ms1 = New System.IO.MemoryStream img.Save(ms1, System.Drawing.Imaging.ImageFormat.Png) Response.ClearContent() '需要输出图象信息 要修改HTTP头 Response.ContentType = "image/Png" Response.BinaryWrite(ms1.ToArray()) g.Dispose() img.Dispose() Response.End() End Sub
函数名称:rndnum
函数参数:vcodenum--设定返回随机字符串的位数
函数功能:产生数字和字符混合的随机字符串
Function rndnum(ByVal vcodenum) '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" Dim vchar As String = "2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,J,K,L,N,P,Q,R,S,T,U,X,Y,Z" Dim vcarray() As String = Split(vchar, ",") '将字符串生成数组 Dim vnum As String = "" Dim i As Byte For i = 1 To vcodenum Randomize() 'vnumvnum = vnum & vcarray(Int(35 * Rnd())) '数组一般从0开始读取，所以这里为35*rnd vnumvnum = vnum & vcarray(Int(29 * Rnd())) '数组一般从0开始读取，所以这里为35*rnd Next Return vnum End Function 以上就是VB.NET中怎么生成验证码，小编相信有部分知识点可能是我们日常工作会见到或用到的。希望你能通过这篇文章学到更多知识。更多详情敬请关注亿速云行业资讯频道。
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