CaptchaMVC6.DefaultCodeGenerator.Generate C# (CSharp) Method

        public string Generate(int length)
        {
            string s = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
            string str = "";
            Random r = new Random();
            for (int i = 0; i < length; i++)
            {
                str += s.Substring(r.Next(s.Length), 1);
            }
            return str;
        }