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1.先写一个方法产生0—9，a-z 35个字符的不重复的随机数，并且位数作为参数传递
/// <summary>
///产生指定位数的随机数
/// </summary>
/// <param name="VcodeNum">产生几位数</param>
/// <returns></returns>
private string RndNum(int VcodeNum)
{
string Vchar = "0,1,2,3,4,5,6,7,8,9";
Vchar = 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";
Vchar = Vchar.ToLower();
string[] VcArray = Vchar.Split(',');
string VNum = "";//由于字符串很短，就不用StringBuilder了
int temp = -1;//记录上次随机数值，尽量避免生产几个一样的随机数
//采用一个简单的算法以保证生成随机数的不同
Random rand = new Random();
for (int i = 1; i < VcodeNum + 1; i++)
{
if (temp != -1)
{
rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));
}
int t = rand.Next(35);
if (temp != -1 && temp == t)
{
return RndNum(VcodeNum);
}
temp = t;
VNum += VcArray[t];
}
return VNum;
}2.然后定义一个方法 绘制验证码
/// <summary>
/// 创建指定数组的验证码
/// </summary>
/// <param name="checkCode">验证码</param>
private void CreateImage(string checkCode)
{
int iwidth = (int)(checkCode.Length * 15);
System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 25);
Graphics g = Graphics.FromImage(image);
g.Clear(Color.White);
//定义颜色
Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Brown, Color.DarkCyan, Color.Purple, Color.YellowGreen };
//定义字体
string[] font = { "Times New Roman", "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
Random rand = new Random();
//随机输出噪点
for (int i = 0; i < 50; i++)
{
int x = rand.Next(image.Width);
int y = rand.Next(image.Height);
//g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1);
g.DrawLine(new Pen(Color.LightPink, 0), x, y, 50, 23);
}
//输出不同字体和颜色的验证码字符
for (int i = 0; i < checkCode.Length; i++)
{
int cindex = rand.Next(7);//从7种颜色中随机取
int findex = rand.Next(6);//从6种字体中随机取
Font f = new System.Drawing.Font(font[findex], 13, System.Drawing.FontStyle.Regular);
Brush b = new System.Drawing.SolidBrush(c[cindex]);
int ii = 4;
//偶数时生成的字符宽度为4，奇数时为2
if ((i + 1) % 2 == 0)
{
ii = 2;
}
g.DrawString(checkCode.Substring(i, 1), f, b, 3 + (i * 12), ii);
}
//画一个边框
g.DrawRectangle(new Pen(Color.Black, 0), 0, 0, image.Width - 1, image.Height - 1);
//输出到浏览器
System.IO.MemoryStream ms = new System.IO.MemoryStream();
image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
Response.ClearContent();
Response.ContentType = "image/Jpeg";
Response.BinaryWrite(ms.ToArray());
g.Dispose();
image.Dispose();
}3.在page_load事件中测试
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
string Code = this.RndNum(4);
Session["Code"] = Code;
this.CreateImage(Code);
}
}来源：时间去哪儿了博客（微信/QQ号：903918446），转载请保留出处和链接！
本文链接：http://timegowhere.com/post/Verification_code.html
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本文标签：生成验证码
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