Verification code source code

First:

Using system. drawing;

Public partial class _ default: system. Web. UI. Page
{
Protected void page_load (Object sender, eventargs E)
{
Createcheckcodeimage (generatecheckcode ());
}

Private string generatecheckcode ()
{
// Create an integer variable
Int number;
// Create a variable
Char code;
// Create a string variable and initialize it as null
String checkcode = string. empty;
// Create a random object
Random random = new random ();
// Use the for loop to generate four numbers
For (INT I = 0; I <4; I ++)
{
// Generate a random number
Number = random. Next ();
// Convert the number to the numeric type
Code = (char) ('0' + (char) (Number % 10 ));

Checkcode + = code. tostring ();
}
// Add the generated random number to cookies
Response. Cookies. Add (New httpcookie ("checkcode", checkcode ));
// Return a string
Return checkcode;
}

Private void createcheckcodeimage (string checkcode)
{
// Judge whether the string is not equal to null or null
If (checkcode = NULL | checkcode. Trim () = string. Empty)
Return;
// Create a bitmap object
System. Drawing. bitmap image = new system. Drawing. Bitmap (INT) math. Ceiling (checkcode. length * 12.5), 22 );
// Create a graphics object
Graphics G = graphics. fromimage (image );

Try
{
// Generate a random Generator
Random random = new random ();

// Clear the background color of the image
G. Clear (color. White );

// Draw the background noise line of the image
For (INT I = 0; I <2; 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. Black), X1, Y1, X2, Y2 );
}

Font font = new system. Drawing. Font ("Arial", 12, (system. Drawing. fontstyle. Bold ));
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 );

// Foreground noise of the image
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 ()));
}

// Draw the border line of the image
G. drawrectangle (new pen (color. Silver), 0, 0, image. Width-1, image. Height-1 );

// Output the image to the page
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 ();
}
}
}

Second:

Protected void page_load (Object sender, eventargs E)
{
If (! Ispostback)
{
Label1.text = randomnum (4); // generate a verification code
}
}
Public String randomnum (int n)
{

String strchar = ", 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, 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 [] vcarray = strchar. Split (',');
String vnum = "";
Int temp =-1; // record the last random value, and try to avoid several identical random numbers.
// Use a simple algorithm to ensure different random numbers are generated
Random Rand = new random ();
For (INT I = 1; I <n + 1; I ++)
{
If (temp! =-1)
{
Rand = new random (I * temp * (INT) datetime. Now. ticks );
}
Int T = Rand. Next (61 );
If (temp! =-1 & temp = T)
{
Return randomnum (N );
}
Temp = T;
Vnum + = vcarray [T];
}
Return vnum; // return the generated random number.
}

Third:

Using system. drawing;
Using system. Drawing. imaging;

Public partial class _ default: system. Web. UI. Page
{
Protected void page_load (Object sender, eventargs E)
{
Session ["code"] = randnum (4 );
Validatecode (session ["code"]. tostring (), 40, 20, "", 10, "# ffffff ");
}
Private string randnum (INT vcodenum)
{
String vchar = ";
String [] vcarray = vchar. Split (','); // split it into an array
String vnum = "";
Int temp =-1; // record the previous random value. Avoid producing several identical random numbers.

Random Rand = new random ();
// Use a simple algorithm to ensure different random numbers are generated
For (INT I = 0; I <vcodenum; I ++)
{
If (temp! =-1)
{
Rand = new random (I * temp * unchecked (INT) datetime. Now. ticks ));
}

Int T = Rand. Next (vcarray. Length-1 );
If (temp! =-1 & temp = T)
{
Return randnum (vcodenum );

}
Temp = T;
Vnum + = vcarray [T];
}
Return vnum;
}

Private void validatecode (string vnum, int W, int H, string font, int fontsize, string bgcolor)
{
Bitmap IMG = new Bitmap (W, H); // instance for generating the image
Graphics G = graphics. fromimage (IMG); // generate a new graphics object from the IMG object
G. Clear (colortranslator. fromhtml (bgcolor); // background color
Font F = new font (font, fontsize); // generate a font class instance
Solidbrush S = new solidbrush (color. Black); // generates an instance of the brush class
G. drawstring (vnum, F, S, 3, 3); // write vnum to the image
IMG. Save (response. outputstream, imageformat. JPEG); // Save the image as a JPEG image file to the stream.
Response. contenttype = "image/JPEG ";
// Reclaim Resources
G. Dispose ();
IMG. Dispose ();
Response. End ();
}

}