Digital Verification Code

// Validatecode. aspx. CS
Using system;
Using system. collections;
Using system. componentmodel;
Using system. Data;
Using system. drawing;
Using system. Web;
Using system. Web. sessionstate;
Using system. Web. UI;
Using system. Web. UI. webcontrols;
Using system. Web. UI. htmlcontrols;
Using system. IO;
Using system. Drawing. imaging;
Using system. configuration;
Namespace yanzhengma
{
/// <Summary>
/// Summary of validatecode.
/// </Summary>
Public class validatecode: system. Web. UI. Page
{
Private void page_load (Object sender, system. eventargs E)
{
If (! Ispostback)
{
// Read the string length from the configuration file
Int num = convert. toint32 (configurationsettings. etettings ["num"]);
String str_validatecode = getrandomnumberstring (Num );
// The session used for verification
Session ["validatecode"] = str_validatecode;
Createimage (str_validatecode );
}
}

Public String getrandomnumberstring (INT int_numberlength)
{
String str_number = string. empty;
Random therandomnumber = new random ();

For (INT int_index = 0; int_index <int_numberlength; int_index ++)
Str_number + = therandomnumber. Next (10). tostring ();

Return str_number;
}
// Generate random colors
Public color getrandomcolor ()
{
Random randomnum_first = new random (INT) datetime. Now. ticks );
// There is nothing to say about the random number of C #.
System. Threading. thread. Sleep (randomnum_first.next (50 ));
Random randomnum_sencond = new random (INT) datetime. Now. ticks );

// Try to generate a dark color for display on a white background
Int int_red = randomnum_first.next (256 );
Int int_green = randomnum_sencond.next (256 );
Int int_blue = (int_red + int_green> 400 )? 0: 400-int_red-int_green;
Int_blue = (int_blue & gt; 255 )? 255: int_blue;

Return color. fromargb (int_red, int_green, int_blue );
}

Public void createimage (string str_validatecode)
{< br> int int_imagewidth = str_validatecode.length * 13;
random newrandom = new random ();
// A 20px bitmap object with a height of 20 PX is used to process images defined by pixel data.
bitmap thebitmap = new Bitmap (int_imagewidth, 20);
// graphics. fromimage creates a new graphics object.
graphics thegraphics = graphics. fromimage (thebitmap);
// white background
thegraphics. clear (color. white);
// The gray border thegraphics. drawrectangle draws a rectangular pen (paint brush color, paint width)
// drawrectangle (paint brush, X, Y, width, heigth)
thegraphics. drawrectangle (new pen (color. lightgray, 1), 0, 0, int_imagewidth-1, 19);
// font of 10pt
font thefont = new font ("Arial ", 10);

For (INT int_index = 0; int_index <str_validatecode.length; int_index ++)
{
// Substring (1, j) Take characters whose length is J from I
String str_char = str_validatecode.substring (int_index, 1 );
// Call the random returned color Method
Brush newbrush = new solidbrush (getrandomcolor ());
// Point (I, j) I horizontal position of the point, vertical position of the Point J
Point thepos = new point (int_index * 13 + 1 + newrandom. Next (3), 1 + newrandom. Next (3 ));
Thegraphics. drawstring (str_char, thefont, newbrush, thepos );
}

// Send the generated image back to the client
Memorystream MS = new memorystream ();
Thebitmap. Save (MS, imageformat. PNG); // save to the specified stream in the specified format

response. clearcontent (); // You Need to output the image information to modify the HTTP header
response. contenttype = "image/PNG";
response. binarywrite (Ms. toarray (); // write a binary string to the HTTP output stream
thegraphics. dispose (); // release all resources used by this graphics object.
thebitmap. Dispose ();
response. End ();
}

# Generated by region web Form DesignerCode
Override protected void oninit (eventargs E)
{
//
// Codegen: This call is required by the ASP. NET web form designer.
//
Initializecomponent ();
Base. oninit (E );
}

/// <Summary>
/// The designer supports the required methods-do not use the code editor to modify
/// Content of this method.
/// </Summary>
Private void initializecomponent ()
{
This. Load + = new system. eventhandler (this. page_load );

}
# Endregion
}
}

// Add the following code to the page for verification:
Private void cmdsubmit_click (Object sender, system. eventargs E)
{
If (txtnum. Text = session ["validatecode"]. tostring ())
{
Response. Write ("OK ");
}
Else
{
Response. Write ("wrong ");
}
}