How to implement a window verification code in the WinForm login form of C #

C # WinForm can develop QQ chat program, chat login Form Verification code is how to achieve it? In WinForm, you need to add your own control to a PictureBox control pbverifycode a button Butupdateverifycode code as follows:  public partial  class frmlogin : form    {        / /Random Code length         private const int iverifycodelength  = 6;        //Random Code          private String strVerifyCode =  "";         Public frmlogin ()         {             initializecomponent ();             updateverifycode ();        }         //Update Verification Code          privatE void updateverifycode ()         {             strverifycode = createrandomcode (iVerifyCodeLength);             createimage (StrVerifyCode);         }        private string  createrandomcode (int ilength)         {             int rand;             char code;             string randomCode = String.Empty;             //generate a certain length of verification code              System.random random&nbsP;= new random ();            for  ( int i = 0; i < ilength; i++)              {                 rand = random. Next ();           if  (rand % 3 ==  0)                 {                      code =  (char) (' A '  +  (char) (rand % 26));                 }                 else                {                     code =  (char) (' 0 '  +  (char) (RAND&NBSP;%&NBSP;10));                 }                 randomcode += code. ToString ();            }             return randomCode;         }        ///   Create random code images          private void createimage (String strverifycode)            {            try            {                 int iRandAngle =  45;    //Random Rotation angle                  int iMapWidth =  (int) (STRVERIFYCODE.LENGTH&NBSP;*&NBSP;21);                 bitmap map =  new bitmap (imapwidth, 28);      //Create picture background                                   graphics graph = graphics.fromimage (map);                 graph. Clear (Color.aliceblue);//Erase PictureFace, fills the background                 graph. DrawRectangle (New pen (color.black, 0),  0, 0, map. Width - 1, map. HEIGHT&NBSP;-&NBSP;1);//Draw a border                  graph. smoothingmode = system.drawing.drawing2d.smoothingmode.antialias;//Mode                  random rand = new random ();                 //background noise generation                 Pen  Blackpen = new pen (color.lightgray, 0);                 for  (int i = 0; i < 50;  i++)        {                     int x = rand. Next (0, map. Width);                     int y = rand. Next (0, map. Height);                     graph. DrawRectangle (blackpen, x, y, 1, 1);                 }                 //verification code rotation to prevent machine identification                  char[] chars = strverifycode.tochararray ();//break string into a single character array                  //          in text distance        stringformat format = new stringformat ( Stringformatflags.noclip);                 format. alignment = stringalignment.center;                 format. linealignment = stringalignment.center;                 //Defining Colors                  Color[] c = { Color.Black, Color.Red,  Color.darkblue, color.green, color.orange, color.brown, color.darkcyan, color.purple  };                //Defining Fonts                  string[] font = {  "Verdana",  "Microsoft sans serif",  "Comic  sans ms ", " Arial ", " Song Body  };              for  (Int i = 0; i < chars. length; i++)                  {                     int cindex = rand. Next (7);                     int findex = rand. Next (5);                     font f = new systEm. Drawing.font (font[findex], 13, system.drawing.fontstyle.bold);//font style (parameter 2 is font size)                      brush  b = new system.drawing.solidbrush (C[cindex]);                     point dot = new  point (16, 16);                                          float angle = rand. Next (-irandangle, irandangle);//degree of rotation                      graph. TranslateTransform (dot. X, dot. Y);//move cursor to the specified position         &nbsP;           graph. RotateTransform (angle);                     graph. DrawString (Chars[i]. ToString (),  f, b, 1, 1, format);                                          graph. RotateTransform (-angle);//Turn Back                      graph. TranslateTransform (2, -dot. Y);//move cursor to the specified position                }                  pbverifycode.image = map;                             }            catch   (ArgumentException)             {                 messagebox.show ("Create picture error. ");            }         }         private void  Butupdateverifycode_click (object sender, eventargs e)          {            updateverifycode ();   The       }            code is all written.

How to implement a window verification code in the WinForm login form of C #