آموزش ساخت کد Captcha در ASP.net - نسخه‌ی قابل چاپ

کد:

//ایجاد شیء گرافیک و دیگر ملزومات

                   Bitmap objBMP = new System.Drawing.Bitmap(80, 25);

                   Graphics objGraphics = System.Drawing.Graphics.FromImage(objBMP);

                   objGraphics.Clear(Color.DarkBlue);

                   objGraphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;

                     //تنظیم فونت نوشته روی عکس

                   Font objFont = new Font("Viner Hand ITC", 13, FontStyle.Bold);

                    //ساخت رشته تصادفی ۵ رقمی 

                   string randomStr = "";

                   Random autoRand = new Random();

                   randomStr = Convert.ToString(autoRand.Next(12345,99999));

             

                   //اضافه کردن متن در جلسه 

                   Session.Add("randomStr", randomStr);

             

                   //نوشتن متن

                   objGraphics.DrawString(randomStr, objFont, Brushes.White, 6, 3);

             

                   //تنظیم نوع عکس و برگرداندن آن به عنوان خروجی

                   Response.ContentType = "image/GIF";

                   objBMP.Save(Response.OutputStream,System.Drawing.Imaging.ImageFormat.Gif);

             

                   //آزاد کردن منابع

                   objFont.Dispose();

                   objGraphics.Dispose();

                   objBMP.Dispose();

کد:

if (TxtCaptcha.Text != "")

        {

            if ((string)Session["randomStr"] == TxtCaptcha.Text.Trim())

            {

                //Submit Form

                Label1.Text = "Captcha is Correct";

                



            }

            else

            {

                //Show Error - Please Enter Security Code that show in Image

                Label1.Text = "Captcha isn't Correct";

            }

        }

        else

        {

            

            Label1.Text = "Please Enter the Captcha!";

        }