1-) C# - captcha kullanımı

 Random random = new Random();

            string[] sembol1 = {"a","b","c","d","e","f","g"};

            string[] sembol2 = {"+","-","*","/",""};

            int s1, s2,s3;

            s1 = random.Next(0,sembol1.Length);

            s2 = random.Next(0,sembol2.Length);

            s3 = random.Next(0,10);

            label1.Text = sembol1[s1].ToString() + sembol2[s2].ToString() + s3.ToString();