System.Web.HttpRequest.IsInvalidString C# (CSharp) Method

		internal static bool IsInvalidString (string val, out int validationFailureIndex)
		{
			validationFailureIndex = 0;

			int len = val.Length;
			if (len < 2)
				return false;

			char current = val [0];
			for (int idx = 1; idx < len; idx++) {
				char next = val [idx];
				// See http://secunia.com/advisories/14325
				if (current == '<' || current == '\xff1c') {
					if (next == '!' || next < ' '
					    || (next >= 'a' && next <= 'z')
					    || (next >= 'A' && next <= 'Z')) {
						validationFailureIndex = idx - 1;
						return true;
					}
				} else if (current == '&' && next == '#') {
					validationFailureIndex = idx - 1;
					return true;
				}

				current = next;
			}

			return false;
		}