Use C # To generate a verification code

First, add a page named code. aspx.
Add namespace

using System.IO;using System.Drawing.Imaging;using System.Drawing.Drawing2D;using System.Drawing;

Add page Initialization

Protected void page_load (Object sender, eventargs e) {// generate a string code = This. createrandomcode (4); // use session to save session ["checkcode"] = Code; // plot createimage (CODE );}

In the code above, createrandomcode is used to generate a random number of specified digits, while createimage is used to draw a pattern. Let's take a look at these two methods:

Createrandomcode:

public string CreateRandomCode(int codeCount){    string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";    string[] allCharArray = allChar.Split(',');    string randomCode = "";    int temp = -1;    Random rand = new Random();    for (int i = 0; i < codeCount; i++)    {        if (temp != -1)        {            rand = new Random(i * temp * ((int)DateTime.Now.Ticks));        }        int t = rand.Next(36);        if (temp != -1 && temp == t)        {            return CreateRandomCode(codeCount);        }        temp = t;        randomCode += allCharArray[t];    }    return randomCode;}

Createimage code:

Private void createimage (string checkcode) {int iwidth = (INT) (checkcode. length * 15); system. drawing. bitmap image = new system. drawing. bitmap (iwidth, 25); graphics G = graphics. fromimage (image); G. clear (color. white); // define the color [] C = {color. black, color. red, color. darkblue, color. green, color. orange, color. brown, color. darkcyan, color. purple}; // define the font string [] font = {"verdana", "Microsoft sans serif", "Comic Sans MS", "Arial", ""}; random Rand = new random (); // random output noise for (INT I = 0; I <50; I ++) {int x = Rand. next (image. width); int y = Rand. next (image. height); G. drawrectangle (new pen (color. lightgray, 0), X, Y, 1, 1) ;}// the verification code character for (INT I = 0; I <checkcode. length; I ++) {int cIndex = Rand. next (7); int findex = Rand. next (5); font F = new system. drawing. font (font [findex], 10, system. drawing. fontstyle. bold); brush B = new system. drawing. solidbrush (C [cIndex]); int II = 4; If (I + 1) % 2 = 0) {II = 2;} G. drawstring (checkcode. substring (I, 1), F, B, 3 + (I * 12), II);} // draw a border G. drawrectangle (new pen (color. black, 0), 0, 0, image. width-1, image. height-1); // output to the browser system. io. memorystream MS = new system. io. memorystream (); image. save (MS, system. drawing. imaging. imageformat. JPEG); response. clearcontent (); response. c; response. binarywrite (Ms. toarray (); G. dispose (); image. dispose ();}

The complete code is provided below

Using system; using system. data; using system. configuration; using system. collections; using system. web; using system. web. security; using system. web. ui; using system. web. UI. webcontrols; using system. web. UI. webcontrols. webparts; using system. web. UI. htmlcontrols; using system. io; using system. drawing. imaging; using system. drawing. drawing2d; using system. drawing; public partial class code: system. web. UI. page {prot Ected void page_load (Object sender, eventargs e) {// generate a string code = This. createrandomcode (4); // use session to save session ["checkcode"] = Code; // map createimage (CODE);} private void createimage (string checkcode) {int iwidth = (INT) (checkcode. length * 15); system. drawing. bitmap image = new system. drawing. bitmap (iwidth, 25); graphics G = graphics. fromimage (image); G. clear (color. white); // define the color [] C = {color. black, color. red, color. darkblue, color. green, color. orange, color. brown, color. darkcyan, color. purple}; // define the font string [] font = {"verdana", "Microsoft sans serif", "Comic Sans MS", "Arial", ""}; random Rand = new random (); // random output noise for (INT I = 0; I <50; I ++) {int x = Rand. next (image. width); int y = Rand. next (image. height); G. drawrectangle (new pen (color. lightgray, 0), X, Y, 1, 1);} // output the verification code characters of different fonts and colors for (INT I = 0; I <checkcode. length; I ++) {int cIndex = Rand. next (7); int findex = Rand. next (5); font F = new system. drawing. font (font [findex], 10, system. drawing. fontstyle. bold); brush B = new system. drawing. solidbrush (C [cIndex]); int II = 4; If (I + 1) % 2 = 0) {II = 2;} G. drawstring (checkcode. substring (I, 1), F, B, 3 + (I * 12), II);} // draw a border G. drawrectangle (New Pen (color. black, 0), 0, 0, image. width-1, image. height-1); // output to the browser system. io. memorystream MS = new system. io. memorystream (); image. save (MS, system. drawing. imaging. imageformat. JPEG); response. clearcontent (); response. c; response. binarywrite (Ms. toarray (); G. dispose (); image. dispose ();} Public String createrandomcode (INT codecount) {string allchar = ", A, B, C, D, E, F, g, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z "; string [] allchararray = allchar. split (','); string randomcode = ""; int temp =-1; random Rand = new random (); For (INT I = 0; I <codecount; I ++) {If (temp! =-1) {Rand = new random (I * temp * (INT) datetime. now. ticks);} int T = Rand. next (36); If (temp! =-1 & temp = T) {return createrandomcode (codecount);} temp = T; randomcode + = allchararray [T];} return randomcode ;}}