asp.net实现网站验证码功能

一、验证码简介

验证码功能一般是用于防止批量注册的，不少网站为了防止用户利用机器人自动注册、登录、灌水，都采用了验证码技术。所谓验证码，就是将一串随机产生的数字或字母或符号或文字，生成一幅图片， 图片里加上一些干扰象素（防止OCR），由用户肉眼识别其中的验证码信息，输入表单提交网站验证，验证成功后才能使用某项功能。

常见的验证码有如下几种：

1、纯数字验证码，一般为四位随机数字；

2、数字+字母验证码，一般从数字（0~9）和字母(A~Z和a~z)中随机抽出几个字符组成；

3、汉字验证码，相对而言，这种验证码比较少见一点，实现起来也相对复杂一些，但在不少网站中还是可以看到的；

二、验证码的实现

1、纯数字验证码的实现

纯数字验证码的实现相对比较简单，可通过以下两种方法来实现

（1）使用随机数方式，代码如下：

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private String GetRandomint(int codeCount)

{

Random random = new Random();

string min = "";

string max = "";

for (int i = 0; i < codeCount; i++)

{

min +="1";

max+="9";

}

return (random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());

}

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private string CreateRandomCode(int codeCount)

{

string allChar = "0,1,2,3,4,5,6,7,8,9";

string[] allCharArray = allChar.Split(',');

string randomCode = "";

int temp = -1;

Random rand = new Random();

for (int i = 0; i < codeCount; i++)

{

if (temp != -1)

{

rand = new Random(i * temp * ((int)DateTime.Now.Ticks));

}

int t = rand.Next(9);

if (temp == t)

{

return CreateRandomCode(codeCount);

}

temp = t;

randomCode += allCharArray[t];

}

return randomCode;

}

private string CreateRandomCode(int codeCount)
{
string allChar = "0,1,2,3,4,5,6,7,8,9";
string[] allCharArray = allChar.Split(',');
string randomCode = "";
int temp = -1;
Random rand = new Random();
for (int i = 0; i < codeCount; i++)
{
if (temp != -1)
{
rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
}
int t = rand.Next(9);
if (temp == t)
{
return CreateRandomCode(codeCount);
}
temp = t;
randomCode += allCharArray[t];
}
return randomCode;
}

2、数字+字母验证码的实现，代码如下：

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private string CreateRandomCode(int codeCount)

{

string allChar = "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,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[] allCharArray = allChar.Split(',');

string randomCode = "";

int temp = -1;

Random rand = new Random();

for (int i = 0; i < codeCount; i++)

{

if (temp != -1)

{

rand = new Random(i * temp * ((int)DateTime.Now.Ticks));

}

int t = rand.Next(61);

if (temp == t)

{

return CreateRandomCode(codeCount);

}

temp = t;

randomCode += allCharArray[t];

}

return randomCode;

}

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/**/

/* 此函数在汉字编码范围内随机创建含两个元素的十六进制字节数组，每个字节数组代表一个汉字，并将

四个字节数组存储在object数组中。

参数：strlength，代表需要产生的汉字个数

*/

public 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();

//定义一个object数组用来

object[] bytes = new object[strlength];

/**/

/*每循环一次产生一个含两个元素的十六进制字节数组，并将其放入bject数组中

每个汉字有四个区位码组成

区位码第1位和区位码第2位作为字节数组第一个元素

区位码第3位和区位码第4位作为字节数组第二个元素

*/

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);//更换随机数发生器的种子避免产生重复值

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);

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;

}

/**/
/* 此函数在汉字编码范围内随机创建含两个元素的十六进制字节数组，每个字节数组代表一个汉字，并将
四个字节数组存储在object数组中。
参数：strlength，代表需要产生的汉字个数
*/
public 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();
//定义一个object数组用来
object[] bytes = new object[strlength];
/**/
/*每循环一次产生一个含两个元素的十六进制字节数组，并将其放入bject数组中
每个汉字有四个区位码组成
区位码第1位和区位码第2位作为字节数组第一个元素
区位码第3位和区位码第4位作为字节数组第二个元素
*/
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);//更换随机数发生器的种子避免产生重复值
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);
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;
}

三、具体实例

前台代码display.aspx

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<body>

<form id="form1" runat="server">

<div>

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

<asp:Image ID="Image1" runat="server" ImageUrl="png.aspx" /><br />

<br />

<asp:Button ID="Button2" runat="server" OnClick="Button2_Click" Text="Button" />

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">

<asp:ListItem Value="3">默认</asp:ListItem>

<asp:ListItem Value="1">文字</asp:ListItem>

<asp:ListItem Value="2">数字</asp:ListItem>

<asp:ListItem Value="3">混合</asp:ListItem>

</asp:DropDownList></div>

</form>

</body>

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protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)

{

switch (DropDownList1.SelectedValue)

{

case "1":

Image1.ImageUrl = "png.aspx?aa=1";

break;

case "2":

Image1.ImageUrl = "png.aspx?aa=2";

break;

case "3":

Image1.ImageUrl = "png.aspx?aa=3";

break;

}

}

protected void Button2_Click(object sender, EventArgs e)

{

if (TextBox1.Text == Session["gif"].ToString())

Response.Write("OK,正确");

else

Response.Write("验证码不符合");

}

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
switch (DropDownList1.SelectedValue)
{
case "1":
Image1.ImageUrl = "png.aspx?aa=1";
break;
case "2":
Image1.ImageUrl = "png.aspx?aa=2";
break;
case "3":
Image1.ImageUrl = "png.aspx?aa=3";
break;
}
}
protected void Button2_Click(object sender, EventArgs e)
{
if (TextBox1.Text == Session["gif"].ToString())
Response.Write("OK,正确");
else
Response.Write("验证码不符合");
}

后台代码png.cs

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

{

protected void Page_Load(object sender, EventArgs e)

{

switch (Request.QueryString["aa"])

{

case "1":

gif = stxt(10);

Session["gif"] = stxt(10);

break;

case "2":

gif = GetRandomint(4);

Session["gif"] = GetRandomint(4);

break;

case "3":

gif = CreateRandomCode(4);

Session["gif"] = CreateRandomCode(4);

break;

default:

gif = CreateRandomCode(4);

Session["gif"] = CreateRandomCode(4);

break;

}

CreateImage(Session["gif"].ToString());

}

private String GetRandomint(int codeCount)

{

Random random = new Random();

string min = "";

string max = "";

for (int i = 0; i < codeCount; i++)

{

min +="1";

max+="9";

}

return (random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());

}

/**/

/*

此函数在汉字编码范围内随机创建含两个元素的十六进制字节数组，每个字节数组代表一个汉字，并将

四个字节数组存储在object数组中。

参数：strlength，代表需要产生的汉字个数

*/

public 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();

//定义一个object数组用来

object[] bytes = new object[strlength];

/**/

/*每循环一次产生一个含两个元素的十六进制字节数组，并将其放入bject数组中

每个汉字有四个区位码组成

区位码第1位和区位码第2位作为字节数组第一个元素

区位码第3位和区位码第4位作为字节数组第二个元素

*/

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);//更换随机数发生器的种子避免产生重复值

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);

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;

}

private string stxt(int num)

{

Encoding gb = Encoding.GetEncoding("gb2312");

//调用函数产生10个随机中文汉字编码

object[] bytes = CreateRegionCode(num);

string strtxt = "";

//根据汉字编码的字节数组解码出中文汉字

for (int i = 0; i < num; i++)

{

strtxt += gb.GetString((byte[])Convert.ChangeType(bytes[i], typeof(byte[])));

}

return strtxt;

}

/// <summary>

/// 这个是使用字母,数字混合

/// </summary>

/// <param name="VcodeNum"></param>

/// <returns></returns>

private string CreateRandomCode(int codeCount)

{

string allChar = "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,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[] allCharArray = allChar.Split(',');

string randomCode = "";

int temp = -1;

Random rand = new Random();

for (int i = 0; i < codeCount; i++)

{

if (temp != -1)

{

rand = new Random(i * temp * ((int)DateTime.Now.Ticks));

}

int t = rand.Next(61);

if (temp == t)

{

return CreateRandomCode(codeCount);

}

temp = t;

randomCode += allCharArray[t];

}

return randomCode;

}

private void CreateImage(string checkCode)

{

int iwidth = (int)(checkCode.Length * 20);

System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 25);

Graphics g = Graphics.FromImage(image);

Font f = new System.Drawing.Font("Arial", 10, System.Drawing.FontStyle.Bold);

Brush b = new System.Drawing.SolidBrush(Color.White);

//g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);

g.Clear(Color.Black);

g.DrawString(checkCode, f, b, 3, 3);

Pen blackPen = new Pen(Color.Black, 0);

Random rand = new Random();

//for (int i=0;i<5;i++)

//{

// int y = rand.Next(image.Height);

// g.DrawLine(blackPen,0,y,image.Width,y);

//}

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();

}

}

public partial class png : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
switch (Request.QueryString["aa"])
{
case "1":
gif = stxt(10);
Session["gif"] = stxt(10);
break;
case "2":
gif = GetRandomint(4);
Session["gif"] = GetRandomint(4);
break;
case "3":
gif = CreateRandomCode(4);
Session["gif"] = CreateRandomCode(4);
break;
default:
gif = CreateRandomCode(4);
Session["gif"] = CreateRandomCode(4);
break;
}
CreateImage(Session["gif"].ToString());
}
private String GetRandomint(int codeCount)
{
Random random = new Random();
string min = "";
string max = "";
for (int i = 0; i < codeCount; i++)
{
min +="1";
max+="9";
}
return (random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());
}
/**/
/*
此函数在汉字编码范围内随机创建含两个元素的十六进制字节数组，每个字节数组代表一个汉字，并将
四个字节数组存储在object数组中。
参数：strlength，代表需要产生的汉字个数
*/
public 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();
//定义一个object数组用来
object[] bytes = new object[strlength];
/**/
/*每循环一次产生一个含两个元素的十六进制字节数组，并将其放入bject数组中
每个汉字有四个区位码组成
区位码第1位和区位码第2位作为字节数组第一个元素
区位码第3位和区位码第4位作为字节数组第二个元素
*/
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);//更换随机数发生器的种子避免产生重复值
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);
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;
}
private string stxt(int num)
{
Encoding gb = Encoding.GetEncoding("gb2312");
//调用函数产生10个随机中文汉字编码
object[] bytes = CreateRegionCode(num);
string strtxt = "";
//根据汉字编码的字节数组解码出中文汉字
for (int i = 0; i < num; i++)
{
strtxt += gb.GetString((byte[])Convert.ChangeType(bytes[i], typeof(byte[])));
}
return strtxt;
}
/// <summary>
/// 这个是使用字母,数字混合
/// </summary>
/// <param name="VcodeNum"></param>
/// <returns></returns>
private string CreateRandomCode(int codeCount)
{
string allChar = "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,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[] allCharArray = allChar.Split(',');
string randomCode = "";
int temp = -1;
Random rand = new Random();
for (int i = 0; i < codeCount; i++)
{
if (temp != -1)
{
rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
}
int t = rand.Next(61);
if (temp == t)
{
return CreateRandomCode(codeCount);
}
temp = t;
randomCode += allCharArray[t];
}
return randomCode;
}
private void CreateImage(string checkCode)
{
int iwidth = (int)(checkCode.Length * 20);
System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 25);
Graphics g = Graphics.FromImage(image);
Font f = new System.Drawing.Font("Arial", 10, System.Drawing.FontStyle.Bold);
Brush b = new System.Drawing.SolidBrush(Color.White);
//g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);
g.Clear(Color.Black);
g.DrawString(checkCode, f, b, 3, 3);
Pen blackPen = new Pen(Color.Black, 0);
Random rand = new Random();
//for (int i=0;i<5;i++)
//{
// int y = rand.Next(image.Height);
// g.DrawLine(blackPen,0,y,image.Width,y);
//}
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();
}
}

四、效果图展示

验证码数字



验证码数字+字母



验证码汉字