asp.net-mvc-4 - Dbcontext with using-clause in Asp.Net Json-Call

Question

I ran into a problem when switching from the Local Development Server to the Local IIS Server (ASP.NET MVC4) using the following Controller-Method:

  public JsonResult GetJsonData(string Context, string Language)  
    {
       using (KeyValueDBContext db = new KeyValueDBContext())
       {

            var entries = from u in db.KeyValues
                          where ((u.Context == Context) && (u.Language == Language))
                          select u;

            return Json(entries, JsonRequestBehavior.AllowGet);
      }

   }

Using the local server, I received data when calling the method from Javascript without a problem. The method retrieves a collection of basically Key-Value pairs from a database repository and sends them to the client). After switching to IIS I got an Exception telling me that the dbcontext had already been disposed of (although the using clause ends after the return-statement). (NB: Visual Studio also was not able to find JSONSerializer.cs for some reason, but only when the error occurred). Switching to the following version solved the problem completely:

public JsonResult GetJsonData(string Context, string Language)   
    {
        KeyValueDBContext db = new KeyValueDBContext();
        var entries = from u in db.KeyValues
                     where ((u.Context == Context) && (u.Language == Language))
                     select u;

        return Json(entries, JsonRequestBehavior.AllowGet);
   }

In both cases, this was the using-block:

  using System;
  using System.Collections.Generic;
  using System.Data;
  using System.Data.Entity;
  using System.Linq;
  using System.Web;
  using System.Web.Mvc;
  using beepov4.Models; // project-models

My question: Is this an acceptable way to use dbcontext for the purpose of JSON-calls (and dropping the using-clause) or is there a particular downside or hidden problem I should be aware of?

Answer 1

Try reading the entries into memory with entries.ToList() before passing them to Json():

using (KeyValueDBContext db = new KeyValueDBContext())
{
        var entries = from u in db.KeyValues
                      where ((u.Context == Context) && (u.Language == Language))
                      select u;

        return Json(entries.ToList(), JsonRequestBehavior.AllowGet);
}