table>
tr>
td class="style1">
nbsp;(驗證碼測試)/td>
td>
nbsp; asp:Label
ID="Label1" runat="server">/asp:Label>
nbsp;
asp:Image ID="Image1" runat="server" Height="22px" ImageUrl="~/ValidNums.aspx" Width="58px" />nbsp;
asp:Image ID="Image2" runat="server" Height="22px" ImageUrl="~/GetValid.aspx" Width="58px" />/td>
/tr> tr>
td class="style1">
nbsp;
/td>
td>
nbsp;nbsp;asp:Button ID="Button1" runat="server" Text="登錄" OnClick="btnOK_Click" />
nbsp;nbsp;
asp:Button ID="Button2" runat="server" Text="取消" />
/td>
/tr>
/table>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
string getNums = GetVali();
Label1.Text = getNums;
}
}

/// summary>
/// 隨機生成4位數
/// /summary>
/// returns>返回生成的隨機數/returns>
public string GetVali()
{
string strsvali = "0,1,2,3,4,5,6,7,8,9";
string[] ValiArray = strsvali.Split(',');
string ReturnNum = "";
int nums = -1;
Random vrand = new Random();
for (int n = 1; n 5; n++)
{
if (nums != -1)
{
vrand = new Random(n * nums * unchecked((int)DateTime.Now.Ticks));
}
int t = vrand.Next(10);
nums = t;
ReturnNum += ValiArray[t];
}
Session["Valid"] = ReturnNum;
return ReturnNum;
}
protected void btnOK_Click(object sender, EventArgs e)
{
if (Session["Valid"].ToString() == TextBox3.Text)
{
ClientScript.RegisterStartupScript(this.GetType(),"ss","script>alert('您已經成功通過登錄驗證！')/script>");
}
else
{
ClientScript.RegisterStartupScript(this.GetType(), "ss", "script>alert('您輸入的驗證碼錯誤！')/script>");
}
}
}

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Text;
using System.Drawing;

public partial class GetValid : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
string validateNum = GetValids(); //成生4位隨機字符串
CreateImage(validateNum); //將生成的隨機字符串繪成圖片
Session["ValidNums"] = validateNum; //保存驗證碼
}
}
public static string GetValids()
{
//獲取GB2312編碼頁（表）
Encoding gb = Encoding.GetEncoding("gb2312");

//調用函數產生4個隨機中文漢字編碼
object[] bytes = CreateRegionCode(4);

//根據漢字編碼的字節數組解碼出中文漢字

string s = String.Empty;
foreach (object byt in bytes)
{
string str1 = gb.GetString((byte[])Convert.ChangeType(byt, typeof(byte[])));
s = s + str1;
}

//輸出的控制臺
return s;
}
public static object[] CreateRegionCode(int strlength)
{
//定義一個字符串數組儲存漢字編碼的組成元素
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();

//定義一個object數組用來
object[] bytes = new object[strlength];
/*每循環一次產生一個含兩個元素的十六進制字節數組，并將其放入bject數組中
每個漢字有四個區位碼組成
區位碼第1位和區位碼第2位作為字節數組第一個元素
區位碼第3位和區位碼第4位作為字節數組第二個元素
*/
for (int i = 0; i strlength; i++)
{
//區位碼第1位
int r1 = rnd.Next(11, 14);
string str_r1 = rBase[r1].Trim();

//區位碼第2位
rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i);
//更換隨機數發生器的種子避免產生重復值
int r2;
if (r1 == 13)
{
r2 = rnd.Next(0, 8);
}
else
{
r2 = rnd.Next(0, 16);
}
string str_r2 = rBase[r2].Trim();

//區位碼第3位
rnd = new Random(r2 * unchecked((int)DateTime.Now.Ticks) + i);
int r3 = rnd.Next(10, 16);
string str_r3 = rBase[r3].Trim();

//區位碼第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();

//定義兩個字節變量存儲產生的隨機漢字區位碼
byte byte1 = Convert.ToByte(str_r1 + str_r2, 16);
byte byte2 = Convert.ToByte(str_r3 + str_r4, 16);
//將兩個字節變量存儲在字節數組中
byte[] str_r = new byte[] { byte1, byte2 };

//將產生的一個漢字的字節數組放入object數組中
bytes.SetValue(str_r, i);

}

return bytes;

}
//生成圖片
private void CreateImage(string validateNum)
{
if (validateNum == null || validateNum.Trim() == String.Empty)
return;
//生成Bitmap圖像
System.Drawing.Bitmap image = new System.Drawing.Bitmap(validateNum.Length * 12 + 10, 22);
Graphics g = Graphics.FromImage(image);

try
{
//生成隨機生成器
Random random = new Random();

//清空圖片背景色
g.Clear(Color.White);

//畫圖片的背景噪音線
for (int i = 0; i 25; i++)
{
int x1 = random.Next(image.Width);
int x2 = random.Next(image.Width);
int y1 = random.Next(image.Height);
int y2 = random.Next(image.Height);

g.DrawLine(new Pen(Color.Coral), x1, y1, x2, y2);
}

Font font = new System.Drawing.Font("Arial", 8);
System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
g.DrawString(validateNum, font, brush, 2, 2);

//畫圖片的前景噪音點
for (int i = 0; i 100; i++)
{
int x = random.Next(image.Width);
int y = random.Next(image.Height);
image.SetPixel(x, y, Color.FromArgb(random.Next()));
}

//畫圖片的邊框線
g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

System.IO.MemoryStream ms = new System.IO.MemoryStream();
//將圖像保存到指定的流
image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType = "image/Gif";
Response.BinaryWrite(ms.ToArray());
}
finally
{
g.Dispose();
image.Dispose();
}
}
}

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Drawing;

public partial class ValidNums : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
string validateNum = CreateRandomNum(4); //成生4位隨機字符串
CreateImage(validateNum); //將生成的隨機字符串繪成圖片
Session["ValidNums"] = validateNum; //保存驗證碼
}
}
//生成隨機字符串
private string CreateRandomNum(int NumCount)
{
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";
string[] allCharArray = allChar.Split(',');//拆分成數組
string randomNum = "";
int temp = -1;//記錄上次隨機數的數值，盡量避免產生幾個相同的隨機數
Random rand = new Random();
for (int i = 0; i NumCount; i++)
{
if (temp != -1)
{
rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
}
int t = rand.Next(35);
if (temp == t)
{
return CreateRandomNum(NumCount);
}
temp = t;
randomNum += allCharArray[t];
}
return randomNum;
}
//生成圖片
private void CreateImage(string validateNum)
{
if (validateNum == null || validateNum.Trim() == String.Empty)
return;
//生成Bitmap圖像
System.Drawing.Bitmap image = new System.Drawing.Bitmap(validateNum.Length * 12 + 10, 22);
Graphics g = Graphics.FromImage(image);

try
{
//生成隨機生成器
Random random = new Random();

//清空圖片背景色
g.Clear(Color.White);

//畫圖片的背景噪音線
for (int i = 0; i 25; i++)
{
int x1 = random.Next(image.Width);
int x2 = random.Next(image.Width);
int y1 = random.Next(image.Height);
int y2 = random.Next(image.Height);

g.DrawLine(new Pen(Color.Coral), x1, y1, x2, y2);
}

Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
g.DrawString(validateNum, font, brush, 2, 2);

//畫圖片的前景噪音點
for (int i = 0; i 100; i++)
{
int x = random.Next(image.Width);
int y = random.Next(image.Height);
image.SetPixel(x, y, Color.FromArgb(random.Next()));
}

//畫圖片的邊框線
g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

System.IO.MemoryStream ms = new System.IO.MemoryStream();
//將圖像保存到指定的流
image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType = "image/Gif";
Response.BinaryWrite(ms.ToArray());
}
finally
{
g.Dispose();
image.Dispose();
}
}
}