Wcf predicate serialization

Question

I have a WCF service that provides a bunch of methods that return business objects. Under the hood, he has a good repository level that uses interface methods such as this:

IEnumerable<User> GetUsers(Func<User, bool> predicate);

So, if I want all users in this role to be able to do:

var plebs = GetUsers(u => u.Roles.Contains(plebRole));

Now I want to expose this opinion, which can be executed by any filter through the WCF interface. WCF api should be available for non.Net clients, so I want to use (relatively) simple types.

I have a Filter object that contains the property name and value:

[DataContract] public class Filter {
    [DataMember] public string Property { get; set; }
    [DataMember] public string Value { get; set; }
}

So, now I can set the WCF method as follows:

IEnumerable<User> GetUsers(IEnumerable<Filter> filters);

Then I can build predicates based on what goes into client filters. Now this is getting messy:

private static Expression<Func<T, bool>> GetPredicate<T>(Filter filter)
{
  var knownPredicates = GetKnownPredicates<T>(filter.Value);
  var t = typeof(T);
  return knownPredicates.ContainsKey(t) && knownPredicates[t].ContainsKey(filter.Property)
           ? knownPredicates[t][filter.Property]
           : True<T>();
}

private static Dictionary<Type, Dictionary<string, Expression<Func<T, bool>>>> GetKnownPredicates<T>(string value)
{
  // ReSharper disable PossibleNullReferenceException
  return new Dictionary<Type, Dictionary<string, Expression<Func<T, bool>>>>
  {
    {
      typeof (User), new Dictionary<string, Expression<Func<T, bool>>>
      {
        { "Forename", x => (x as User).Forename == value },
        { "IsAdult", x => (x as User).IsAdult.ToString() == value },
        ...
      }
    },
    {
      typeof (Group), new Dictionary<string, Expression<Func<T, bool>>>
      {
        { "Name", x => (x as Group).Name == value },
        ...
      }
    },
    ...
  };
  // ReSharper restore PossibleNullReferenceException
}

GetKnownPredicates, . . ?

Answer 1

-, System.Linq.Expressions.Expression , , , , , , , Filter.Property, Filter.Value. , .

, , , !

Answer 2

, Func<User, bool> . .

, , , u => u.Roles.Contains(plebRole). , , , .