protected void Page_Load(object sender, EventArgs e)
{
//獲取GB2312編碼頁（表）
/**//**
* 生成中文驗(yàn)證驗(yàn)碼所要使用的方法
* 注，生成中文驗(yàn)證碼時(shí)要改變一下生成驗(yàn)證碼圖片的寬度
* var imageCode = new System.Drawing.Bitmap((int)Math.Ceiling((code.Length * 22.5)), 23); //定義圖片的寬度和高度
**/

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

/**/////調(diào)用函數(shù)產(chǎn)生4個(gè)隨機(jī)中文漢字編碼
//object[] bytes = CreateRegionCode(4);

/**/////根據(jù)漢字編碼的字節(jié)數(shù)組解碼出中文漢字
//var sbCode = new StringBuilder().Append(gb.GetString((byte[])Convert.ChangeType(bytes[0], typeof(byte[]))))
// .Append(gb.GetString((byte[])Convert.ChangeType(bytes[1], typeof(byte[]))))
// .Append(gb.GetString((byte[])Convert.ChangeType(bytes[2], typeof(byte[]))))
// .Append(gb.GetString((byte[])Convert.ChangeType(bytes[3], typeof(byte[]))));
//CreateCheckCodeImage(sbCode.ToString());

CreateCheckCodeImage(GenerateCheckCode()); //生成數(shù)字英文所要使用的方法
}

生成漢字驗(yàn)證碼#region 生成漢字驗(yàn)證碼
/**//// <summary>
/// 此函數(shù)在漢字編碼范圍內(nèi)隨機(jī)創(chuàng)建含兩個(gè)元素的十六進(jìn)制字節(jié)數(shù)組，每個(gè)字節(jié)數(shù)組代表一個(gè)漢字，并將四個(gè)字節(jié)數(shù)組存儲在object數(shù)組中。
/// </summary>
/// <param name="strLength">代表需要產(chǎn)生的漢字個(gè)數(shù)</param>
/// <returns></returns>
static object[] CreateRegionCode(int strLength)
{
var rBase = new[]
{
"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"
};

var random = new Random();
var bytes = new object[strLength];

/**//*每循環(huán)一次產(chǎn)生一個(gè)含兩個(gè)元素的十六進(jìn)制字節(jié)數(shù)組，并將其放入bject數(shù)組中
每個(gè)漢字有四個(gè)區(qū)位碼組成
區(qū)位碼第1位和區(qū)位碼第2位作為字節(jié)數(shù)組第一個(gè)元素
區(qū)位碼第3位和區(qū)位碼第4位作為字節(jié)數(shù)組第二個(gè)元素
*/

for (int i = 0; i < strLength; i++)
{
//區(qū)位碼第1位
var r1 = random.Next(11, 14);
var str_r1 = rBase[r1].Trim();

random = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i); //更換隨機(jī)數(shù)發(fā)生器的種子避免產(chǎn)生重復(fù)值

var r2 = 0;
if (r1 == 13)
r2 = random.Next(0, 7);
else
r2 = random.Next(0, 16);

var str_r2 = rBase[r2].Trim();

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

//區(qū)位碼第4位
random = new Random(r3 * unchecked((int)DateTime.Now.Ticks) + i);
var r4 = 0;
if (r3 == 10)
r4 = random.Next(1, 16);
else if (r3 == 15)
r4 = random.Next(0, 15);
else
r4 = random.Next(0, 16);

var str_r4 = rBase[r4].Trim();

var byte1 = Convert.ToByte(str_r1 + str_r2, 16);
var byte2 = Convert.ToByte(str_r3 + str_r4, 16);
//將兩個(gè)字節(jié)變量存儲在字節(jié)數(shù)組中
var str_r = new[] { byte1, byte2 };

//將產(chǎn)生的一個(gè)漢字的字節(jié)數(shù)組放入object數(shù)組中
bytes.SetValue(str_r, i);
}
return bytes;
}
#endregion

生成圖片#region 生成圖片
void CreateCheckCodeImage(string code)
{
var imageCode = new System.Drawing.Bitmap((int)Math.Ceiling((code.Length * 12.5)), 23); //定義圖片的寬度和高度
var g = Graphics.FromImage(imageCode); //加載圖片到畫布上

try
{
var random = new Random();
g.Clear(Color.White); //清空圖片背景色

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

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

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

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

//畫圖片的邊框線
g.DrawRectangle(new Pen(Color.Silver), 0, 0, imageCode.Width - 1, imageCode.Height - 1);
var ms = new System.IO.MemoryStream();
imageCode.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);

Response.ClearContent();
Response.ContentType = "image/Jpeg";
Response.BinaryWrite(ms.ToArray());
}
finally
{
g.Dispose();
imageCode.Dispose();
}

}
#endregion

生成數(shù)據(jù)驗(yàn)證碼#region 生成數(shù)據(jù)驗(yàn)證碼
private string GenerateCheckCode()
{
int number;
char code;
string checkCode = String.Empty;

var random = new Random();

for (int i = 0; i < 5; i++)
{
number = random.Next();

if (number % 2 == 0)
code = (char)('0' + (char)(number % 10));
else
code = (char)('A' + (char)(number % 26));

checkCode += code.ToString();
}
return checkCode;
}
#endregion

<form id="formCode" runat="server">
<div>
<img src="CheckCode.aspx" src="CheckCode.aspx" alt="驗(yàn)證碼" />
</div>
</form>