protected void Page_Load(object sender, EventArgs e)
{
//調用函數將驗證碼生成圖片
this.CreateCheckCodeImage(GenerateCheckCode());
}
private string GenerateCheckCode()
{ //產生五位的隨機字符串
int number;
char code;
string checkCode = String.Empty;
System.Random 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();
}
//Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
//用於客戶端校驗碼比較
return checkCode;
}
private void CreateCheckCodeImage(string checkCode)
{ //將驗證碼生成圖片顯示
if (checkCode == null || checkCode.Trim() == String.Empty)
return;
Session["CheckCode"] = checkCode;
System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 18.5)), 28);
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.AntiqueWhite);
//畫圖片的背景噪音線
for (int i = 0; i < 10; 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.Silver), x1, y1, x2, y2);
}
Font font = new System.Drawing.Font("Arial", 18, (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(checkCode, 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();
image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType = "image/Gif";
Response.BinaryWrite(ms.ToArray());
}
finally
{
g.Dispose();
image.Dispose();
}
}
private string GenCode(int num)
{
//string str = "的一是在不123456789了Q有和人這Q中大為W上個國我以要他時來E用ASDFGHJKLIUYTREWQZXCVBNM3們生到作地R於出就分對成會可主發年動同工也能下2過子2說產43種ASDFGHJKLIUYTREWQZXCVBNM3面而方後多定行學法0所民得經十三之進著等部度sASDFGHJKLIUYTREWQZXCVBNM3家電力裡如水化高自二k123456789q加量都兩體制機9當使點從業1本去把性3好應開它E合R還因由其D些然前外天政ASDFGHJKLIUYTREWQZXCVBNM3W四日那社E義事平SWQ形RFE相a全h表間樣與關j各重新線內數正心反8你明l看原又麼z利比或T但質123456789氣第4向道命W3此變43條只DF沒結0S解a問A意建8月公0無7系軍很情AUF者4W最立代想D1已L通G並提7g直4L34題H黨123456789程展五U3果料U象員革4位入常文2總次品式活設U及AY管A特件長求w老頭基資5邊流2路F級S少圖3山統接知5TK較S將0組3見計F別她手5角期b根0論ASDFGHJKLIUYTREWQZXCVBNM3油思s術極交受U123456789聯20什認六共S權F收asdecvrrtfghujnmkiolpz證改F清D己美4再采轉更7單SD風5切U8打白J2教速花帶安IM場123456789身車J例真務具萬每目至達G走積r,示345議聲U報N斗完類0八離ASDFGHJKLIUYTREWQ123456789ZXCVBNM3華名確A才SS科張CDXG信U馬節話XZ米U整空Z元Y況D今集a溫傳土許步pGBY群廣J石記asdecvrrtfghujnmk123456789iolpz需段H4研界拉J林律叫K且究O觀越H織K6裝U影casdecvr123456789rtfghujnmkiolpzL算低持v音眾o3書t布A復TV容兒8際商Z非驗連斷HJ深難近礦千周委素M技備半辦V青VT5省PD列n習響B約s支般史d感I勞便團9往5酸歷市克何除消構府u稱太准精值號Zi率族G維XB劃選標C寫存候毛3親快2效M斯Masdecvrrtfghujnmkiolpz3院C查江4型眼5王4B按格5養N易5置M派5層片U始C卻專狀育7廠U京asdecvrrtfghujnmkiolpz識7適屬圓8包火住調m滿縣局7照參紅細引聽該鐵價嚴";
string str = "123456789abcdefghigklmnopqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ";//去掉的O容易混淆的字母
char[] chastr = str.ToCharArray();
// string[] source ={ "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", "V", "W", "X", "Y", "Z", "#", "$", "%", "&", "@" };
string code = "";
Random rd = new Random();
int i;
for (i = 0; i < num; i++)
{
//code += source[rd.Next(0, source.Length)];
code += str.Substring(rd.Next(0, str.Length), 1);
}
return code;
}
前台調用時圖片地址則可寫畫驗證碼的頁字（“~/....aspx”）;
換一張：
<a href="javascript：document.getElementById('ValidateCodeImage').src='ValidateCode.aspx?'+new Date;void(0);">
換一張
</a>
