Strongly type returned JSON using MonoRail

Question

Hi

I am calling the following method in my controller using $.getJSON()

    [return: JSONReturnBinder]
 public object ProfileFields()
 {
  var userfields = _profileSvc.GetFields(282);
  var fields = from f in userfields
               select new {f.ID, f.FieldName};

        return fields;
 }

My _profileSvc comes back with extra data that I don't need (actually I get NHibernate errors because the session is closed).

Is there a better way to do what I am doing? Should I strongly type the data I am returning or is this approach sufficient?

Thanks.

Answer 1

I would use a projection (SetProjection()) and SetResultTransformer() to strongly-type the result to a DTO.

See:

• http://www.nhforge.org/doc/nh/en/index.html#querycriteria-projection
• http://www.junasoftware.com/blog/nhibernate-setresulttransformer-and-dto.aspx
• http://ayende.com/Blog/archive/2007/08/30/Slicing-amp-Dicing-Queries-with-NHibernate.aspx
• http://devlicio.us/blogs/derik%5Fwhittaker/archive/2009/05/27/nhibernate-amp-setprojects-setprojects-w-list-gotcha.aspx

Answer 2

First, I would change the return value of the action to be an IList...

I think that the session closed error may stem from a delayed-execution of 'var fields'. If you change your return statement to fields.ToList(), that will force the execution of the lambda expression and you might get rid of the Session error:

[return: JSONReturnBinder]
    public object ProfileFields()
    {
            var userfields = _profileSvc.GetFields(282);
            var fields = from f in userfields
                         select new {f.ID, f.FieldName};

    return fields.ToList();
    }