asp.net Verification Code Implementation code (C #) _ Practical Tips

public class ValidateCode:System.Web.UI.Page
{
private void Page_Load (object sender, System.EventArgs e)
{
This. Createcheckcodeimage (Generatecheckcode ());
}
Code generated #region the Web forms Designer
Override protected void OnInit (EventArgs e)
{
//
CodeGen: This call is required for the ASP.net Web forms Designer.
//
InitializeComponent ();
Base. OnInit (e);
}

<summary>
Designer supports required methods-do not use the Code editor to modify
The contents of this method.
</summary>
private void InitializeComponent ()
{
This. Load + = new System.EventHandler (this. Page_Load);
}
#endregion
private String Generatecheckcode ()
{
int number;
char code;
string checkcode = String.Empty;
System.Random Random = new Random ();
for (int i=0; i<5; i++)
{
Number = random. Next ();
if (number% 2 = 0)
Code = (char) (' 0 ' + (char) (number% 10));
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)), 22;
Graphics g = graphics.fromimage (image);
Try
{
Generate a random generator
Random Random = new Random ();
Empty picture background color
G.clear (Color.White);
Background noise line for painting pictures
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, y1, x2, y2);
}
Font font = new System.Drawing.Font (Arial), (System.Drawing.FontStyle.Bold | System.Drawing.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);
Picture of the foreground noise point
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 a picture's border line
G.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.c;
Response.BinaryWrite (Ms. ToArray ());
}
Finally
{
G.dispose ();
Image. Dispose ();
}
}
}


If the above Authentication code generator page name is: checkcode.aspx, then uses "
Use the following code to determine the authentication code in the handling event of the login button on the login page:

private void Btnlogin_click (object sender, System.Web.UI.ImageClickEventArgs e)
{
if (request.cookies["checkcode"] = = null)
{
Lblmessage.text = "Your browser settings have been disabled cookies, you must set the browser to allow the use of cookies to use the system." ";
Lblmessage.visible = true;
Return
}
if (String.Compare (request.cookies["Checkcode"). Value, Txtcheckcode.text, True)!= 0)
{
Lblmessage.text = "Wrong authentication code, please enter the correct authentication code." ";
Lblmessage.visible = true;
Return
}

}