using System;

public class Program

{

            private static readonly char[] StartingChars = { '<', '&' };

    public static void Main()

    {

        int test = 0;

        var t = IsDangerousString("<TI Cost reduction on All Hella Global lamps (ID 5918)> test", out test);

        Console.WriteLine(t);

    }

            /// <summary>

        /// IsDangerousString

        /// </summary>

        /// <param name="s">s</param>

        /// <param name="matchIndex">matchIndex</param>

        /// <returns>true/false</returns>

        public static bool IsDangerousString(string s, out int matchIndex)

        {

            // bool inComment = false;

            matchIndex = 0;

​

            for (var i = 0; ;)

            {

                // Look for the start of one of our patterns

                var n = s.IndexOfAny(StartingChars, i);

​

                // If not found, the string is safe

                if (n < 0)

                {

                    return false;

                }

​

                // If it's the last char, it's safe

                if (n == s.Length - 1)

                {

                    return false;

                }

​

                matchIndex = n;

​

                switch (s[n])

                {

                    case '<':

                        // If the < is followed by a letter or '!', it's unsafe (looks like a tag or HTML comment)

                        if (IsAtoZ(s[n + 1]) || s[n + 1] == '!' || s[n + 1] == '/' || s[n + 1] == '?')

                        {

                            return true;

                        }

​

                        break;

                    case '&':

                        // If the & is followed by a #, it's unsafe (e.g. S)

                        if (s[n + 1] == '#')

                        {

                            return true;

                        }

​

                        break;

                }

​

                // Continue searching

                i = n + 1;

            }

        }

        private static bool IsAtoZ(char c)

        {

            return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');

        }

}