Super simple refreshing Verification Code (discard ajax)

First, draw a verification code. This is very simple.

Paste the code

ImageValidate. aspx

Protected void Page_Load (object sender, EventArgs e)
{
// Generate a four-digit Verification Code
CreateCheckCodeImage (GenerateCheckCode ());
}
Private string GenerateCheckCode ()
{
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 ();
}
Session ["CheckCode"] = checkCode;
Return checkCode;
}

Private void CreateCheckCodeImage (string checkCode)
{
If (checkCode = null | checkCode. Trim () = String. Empty)
Return;

System. Drawing. Bitmap image = new System. Drawing. Bitmap (int) Math. Ceiling (checkCode. Length * 12.5), 22 );
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 <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. Silver), 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 (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 );

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 ();
}
}

Then add an img on the login page to display the verification code.

Add an onclick event this. src = '/include/imageValidate. aspx? Id = '+ (Math. random () % 13 );

If you directly write this. src = imageValidate. aspx Therefore, access to this verification code will be cached, so it will not be able to achieve the goal of refreshing.

We add a random address query behind the page so that the page will not be cached by the browser. In this way, the verification code after each click may be different ~