ASP. NET login interface verification code implementation

Recently, I was working on a system. I found a project in my junior year at school. I found something that can be used, for example, the implementation of the login interface verification code. The purpose of the verification code design is to prevent malicious logon. The following can be done in ASP:

1. Create a login page with a verification code input box added, followed by an image. The source address of the image is An ASPX page that generates the verification code.

 
Verification Code: <asp: textbox id = "txtcheckcode" runat = "server" font-names = "" font-size = "medium" width = "113px"> </ASP: textbox> <asp: Image id = "image4" runat = "server" imageurl = "~ /Checkcode. aspx "/>
 

2. Create the checkcode. ASPX page. You only need to add a vertex between the head flag.Code

 
<% Response. buffer = true; %> <% response. expiresabsolute = datetime. now. addseconds (-1); %> <% response. expires = 0; %> <% response. cachecontrol = "no-Cache"; %>
 

3. Add code to the checkcode. aspx. CS page.

First, add a user space:

Using system. Data. sqlclient; using system. drawing;
 

Add the remaining code:

Protected void page_load (Object sender, eventargs e) {createcheckcodeimage (generatecheckcode () ;}// create a verification code private string generatecheckcode () {int number; char code; string checkcode = string. empty; system. random random = new random (); For (INT I = 0; I <6; 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;} // generate the verification code background image private void createcheckcodeimage (string checkcode) {If (checkcode = NULL | checkcode. trim () = string. empty) return; system. drawing. bitmap image = new Bitmap (INT) math. ceiling (checkcode. length * 13.5), 22); graphics G = graphics. fromimage (image); try {// generate random generator random = new random (); // clear the image background color G. clear (color. white); // after all, the noise line 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, x2, Y1, Y2);} Font font = new font ("Arial", 12, (fontstyle. bold | 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 to be painted 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 G of the image. 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 ();}}

At the beginning, this login module was made by a girl. Although I made the core module of the system at that time, and she only made a login module, the final score of others was higher than that of me, my family scored 95, But I scored 90, which is too embarrassing.