The verification code of the letter and man combination, including the function of changing the character

1. Write a verification code. The front-end does not need to write anything. This is the background code of createverificationcode_page.aspx.cs.

Using system;
Using system. collections;
Using system. configuration;
Using system. Data;
Using system. LINQ;
Using system. Web;
Using system. Web. Security;
Using system. Web. UI;
Using system. Web. UI. htmlcontrols;
Using system. Web. UI. webcontrols;
Using system. Web. UI. webcontrols. webparts;
Using system. xml. LINQ;
Using system. drawing;

Namespace Verification Code
{
Public partial class createverificationcode_page: system. Web. UI. Page
{
Protected void page_load (Object sender, eventargs E)
{
// Place user code here to initialize the page
Createcheckcodeimage (generatecheckcode (5); // charnum = 5,
Session ["checkcode"] = generatecheckcode (5 );
}

# Code generated by region web Form Designer
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 the content of this method.
/// </Summary>
Private void initializecomponent ()
{
This. Load + = new eventhandler (page_load );
}
# Endregion

Private string generatecheckcode (INT charnum) // charnum is the number of letters or numbers to be displayed in the verification code
{
Int number;
Char code;
String checkcode = string. empty;
Random random = new random ();
For (INT I = 0; I <charnum; I ++)
{
Number = random. Next ();
If (Number % 2 = 0) // convert it to an ascii code to get the added number and then convert it to a char
{
Int x = Number % 10;
If (x = 0 | x = 1)
{
Code = (char) ('0' + (char) (3 ));
}
Else
{
Code = (char) ('0' + (char) (Number % 10 ));
}
}
Else
{
Int y = Number % 26;
If (y = 8 | Y = 14)
{
Code = (char) ('A' + (char) (0 ));
}
Else
{
Code = (char) ('A' + (char) (Number % 26 ));
}
}
Checkcode + = code. tostring ();
}
// Response. Cookies. Add (New httpcookie ("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), 20); graphics G = graphics. fromimage (image );
Try
{
Random random = new random (); // generate a random Generator
G. Clear (color. White); // clear the background color of the image.
For (INT I = 0; I <2; I ++) // draws the background noise line of the image.
{
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 );
For (INT I = 0; I <100; I ++) // foreground noise of the picture
{
Int x = random. Next (image. width );
Int y = random. Next (image. Height );
Image. setpixel (X, Y, color. fromargb (random. Next ()));
}
G. drawrectangle (new pen (color. Silver), 0, 0, image. Width-1, image. Height-1); // draw the border line of the image
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 ();
}
}

}
}

2. Verification Code Page

(1) login_page.aspx front-end

<Script language = "JavaScript"> // you can't see another implementation.
Function Change ()
{
VaR IMG = Document. getelementbyid ("imgcode ");
IMG. src = IMG. SRC + '? ';
}
</SCRIPT>

<Tr>
<TD align = "right"> verificationcode: </TD>
<TD> <input type = "text" runat = "server" id = "txtcode" style = "width: 128px" maxlength = "4"/> </TD>
<TD>
<Table>
<Tr>
<TD>

</TD>
<TD>
<A href = "javascript: Change ();" style = "font-size: 12px"> notclear? </A> // you can't see another implementation.
</TD>
</Tr>

(2) login_page.aspx.cs background

Protected void btnlogin_click (Object sender, eventargs e) // click Login to verify if the entered verification code is incorrect
{
String checkcode = session ["checkcode"]. tostring ();
If (txtcode. value. Equals (checkcode, stringcomparison. ordinalignorecase) // you can check whether the input is equal to the Verification code.
{
Response. Write ("<SCRIPT> alert ('verification code input correct! ') </SCRIPT> ");
}
Else
{
Page. clientscript. registerclientscriptblock (clientscript. GetType (), "myscript", "<SCRIPT> alert ('verification code input incorrect! ') </SCRIPT> ");
}
}