gistfile1.txt

    //davepermen
    interface IFilterer
    {
        Expression<Func<Message, bool>> Filter(string Value);
    }

    static class Filterer
    {
        static public IFilterer Get(FilterParameterOperatorEnum op)
        {
            var name = System.Enum.GetName(typeof(FilterParameterOperatorEnum), op);
            var type = Type.GetType("ConsoleApplication1." + name + "Filterer"); // needs your namespace right there
            return Activator.CreateInstance(type) as IFilterer;
        }
    }

    class EqualToFilterer : IFilterer
    {
        public Expression<Func<Message, bool>> Filter(string Value)
        {
            return message => !string.IsNullOrEmpty(message.Body) &&
                                      message.Body
                                             .Equals(Value, StringComparison.InvariantCultureIgnoreCase);
        }
    }

    class NotEqualToFilterer : IFilterer
    {
        public Expression<Func<Message, bool>> Filter(string Value)
        {
            return message => !string.IsNullOrEmpty(message.Body) &&
                              !message.Body
                                     .Equals(Value, StringComparison.InvariantCultureIgnoreCase);
        }
    }

    class ContainsFilterer : IFilterer
    {
        public Expression<Func<Message, bool>> Filter(string Value)
        {
            return message =>
                    !string.IsNullOrEmpty(message.Body) &&
                    message.Body.IndexOf(Value,
                                   StringComparison.InvariantCultureIgnoreCase) >= 0;
        }
    }

    class DoesNotContainFilterer : IFilterer
    {
        public Expression<Func<Message, bool>> Filter(string Value)
        {
            return message =>
                    !string.IsNullOrEmpty(message.Body) &&
                    message.Body.IndexOf(Value,
                                    StringComparison.InvariantCultureIgnoreCase) == -1;
        }
    }

    //jchannon
    class MessageFilterer
    {
        private FilterParameterOperatorEnum operatorEnum;
        private string value;

        public Expression<Func<Message, bool>> FilterData()
        {
            var filterer = Filterer.Get(operatorEnum);
            filterer.Filter(value);

            return null;
        }
    }

    enum FilterParameterOperatorEnum
    {
        EqualTo,
        NotEqualTo,
        Contains,
        DoesNotContain
    }

    class Message
    {
        public string Body { get; set; }
    }