x.ToString() is not supported by the entity framework!

Question

Entity framework doesn't recognize my ToString method that converts the route object to specifix string:

public IEnumerable<Route> GetRoutes(string prefix, string searchPattern, string code)
{
    return Routes.
        Where(x => code == null || x.Code == code).
        Where(x => searchPattern == null || x.ToString().Contains(searchPattern)).
        Where(x => prefix == null || x.ToString().StartsWith(prefix));
}

Here is my Route entity:

 public class Route : IDataEntity, ISoftDeletable
    {
        public virtual long Id { get; set; }
        public virtual string Code { get; set; }
        public virtual bool IsDeleted { get; set; }
        public virtual Guid CompanyId { get; set; }
        public virtual IList<LocationInRoute> Locations { get; set; }

        public override string ToString()
        {
            StringBuilder str = new StringBuilder();
            foreach (LocationInRoute loc in Locations)
            {
                if (str.Length > 0)
                {
                    str.Append(" > ");
                }
                str.Append(loc.ToString());
            }
            return str.ToString();
        }
    }

All the x.ToString() throws an exception of not supported in linq to entities.. Any workaround?

Answer 1

You cannot do this on client side (ToString).

You must create SQL function which will do your evaluation - it can either do only string concatenation of you locations (I believe it is related entity) or you can do the whole test in custom function. Then you can import that function into your entity model (EDMX) and create EdmFunctionAttribute to call it - MSDN.