Implementation of the Asp.net 2.0 verification module

1. Build a module and compile it into a DLL.

Namespace aspnetajaxweb. validatecode. Page
{
Public class validatecode: system. Web. UI. Page
{
Private const double imagelengthbase= 12.5;
Private const int imageheigth = 22;
Private const int imagelinenumber = 25;
Private const int imagepointnumber = 100;
Public static string validatecodekey = "validatecodekey ";

Private int length = 4;
Private string code = string. empty;

/// <Summary>
/// Obtain or set the verification code length. The default value is 4.
/// </Summary>
Public int Length
{
Get
{
Return length;
}
Set
{
Length = value;
}
}

/// <Summary>
/// Obtain the verification code
/// </Summary>
Public String code
{
Get
{
Return code;
}
}

Public validatecode ()
{

}

Protected override void onload (eventargs E)
{
Createvalidateimage (length );
}

///

// create a random Verification Code
///
/// Verification code length
//
Public String createcode (INT length)
{< br> If (length <= 0) return string. empty;
// create a random number and construct the Verification Code
random = new random ();
stringbuilder sbcode = new stringbuilder ();
for (INT I = 0; I {< br> sbcode. append (random. next ();
}< br> // Save the verification code to the session object
code = sbcode. tostring ();
session [validatecodekey] = Code;
return code;
}

///

// create an image and Verification Code
///
/// Verification code length
Public void createvalidateimage (INT length)
{// create a Verification Code
code = createcode (length);
// create an image of the Verification Code
createvalidateimage (CODE );
}

/// <Summary>
/// Image and verification code for creating the verification code
/// </Summary>
/// <Param name = "code"> Verification Code </param>
Public void createvalidateimage (string code)
{
If (string. isnullorempty (CODE) = true) return;
/// Save the verification code to the Session Object
Session [validatecodekey] = code;
/// Create an image
Bitmap image = new Bitmap (INT) math. Ceiling (code. length * imagelengthbase), imageheigth );
Graphics G = graphics. fromimage (image );

/// Random number generator
Random random = new random ();

Try
{
/// Clear the image and specify the fill color
G. Clear (color. White );

// draw the interference line of the image
int x1, x2, Y1, Y2;
for (INT I = 0; I {< br> X1 = random. next (image. width);
Y1 = random. next (image. height);
X2 = random. next (image. width);
Y2 = random. next (image. height);
// draw the interference line
G. drawline (new pen (color. silver), X1, Y1, X2, Y2);
}

/// Draw the verification code
Font font = new font ("tahoma", 12, fontstyle. Bold | fontstyle. italic );
Lineargradientbrush brush = new lineargradientbrush (New rectangle (0, 0, image. Width, image. Height ),
Color. Blue, color. darkred, 1.2f, true );
G. drawstring (Code, Font, brush, 2.0f, 2.0f );

/// Foreground noise of the image
Int X, Y;
For (INT I = 0; I <imagepointnumber; I ++)
{
X = random. Next (image. width );
Y = random. Next (image. Height );
/// Draw point
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 );
/// Save the image content to the stream
Memorystream MS = new memorystream ();
Image. Save (MS, imageformat. GIF );
/// Output image
Response. clearcontent ();
Response. contenttype = "image/GIF ";
Response. binarywrite (Ms. toarray ());
}
Finally
{// Release occupied Resources
G. Dispose ();
Image. Dispose ();
}
}
}
}

2. Create a validatecode. ASP page.
<% @ Page Language = "C #" autoeventwireup = "false" inherits = "aspnetajaxweb. validatecode. Page. validatecode" %>
3. reference the compiled DLL where the verification code is to be used.
4. areas to use
<Tr bgcolor = "white">
<TD> Verification Code: </TD>
<TD>
<Asp: textbox id = "tbcode" runat = "server" skinid = "tbskin" width = "80px"> </ASP: textbox>
<Asp: Image id = "imgcode" runat = "server" imageurl = "~ /Validatecode. aspx "/>
</TD>
</Tr>
5 Logic Code
// Determine whether verification is created
If (session [validatecode. validatecodekey] = NULL) return;
/// Verify that the verification code is equal
If (tbcode. Text! = Session [validatecode. validatecodekey]. tostring ())
{
Lbmessage. Text = "Incorrect verification code. Please enter it again. ";
Return;
}