Serializing Entity Framework Objects into JSON

Question

public class GenericHandler : IHttpHandler
{
    public class ASSystem
    {
        public string SID { get; set; }
        public string Description { get; set; }
        public string SystemName { get; set; }
    }

    public class ErrorObj
    {
        public string ErrorMessage { get; set; }
    }

    public void ProcessRequest(HttpContext context)
    {
        HttpContext.Current.Response.ContentType = "application/json";
        HttpContext.Current.Response.ContentEncoding = Encoding.UTF8;

        string query = HttpContext.Current.Request.QueryString["SID"];


        SOFAEntities ctx = new SOFAEntities();
        JavaScriptSerializer serializer = new JavaScriptSerializer();

        try
        {
            AS_SYSTEM system = ctx.AS_SYSTEM.Where(s => s.SYSTEM_ID == query).First() as AS_SYSTEM;

            if (system != null)
            {
                ASSystem sys = new ASSystem() { SID = system.SYSTEM_ID, Description = system.DESCRIPTION, SystemName = system.SYSTEM_NAME };
                HttpContext.Current.Response.Write(serializer.Serialize(sys));
            }
        }
        catch (Exception e)
        {
            HttpContext.Current.Response.Write(serializer.Serialize(new ErrorObj() { ErrorMessage = e.Message }));
        }





    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }
}

This works, but when i try with HttpContext.Current.Response.Write(serializer.Serialize(system)); i get the following error:

A circular reference was detected while serializing an object of type 'System.Data.Metadata.Edm.AssociationType

What i wanted was a json object representating the complete as_system object, so i dont have to map each property manually. Is there any way to solve this? Thanks!

Hamid Nasirloo · Accepted Answer · 2016-05-19 11:45:41Z

5

If you want Serialize Entity Framework Objects into JSON, You can use JSON.NET from http://www.newtonsoft.com. to do this, install JSON.NET from nuget and use following code sample:

return Newtonsoft.Json.JsonConvert.SerializeObject(results, Formatting.Indented, 
new JsonSerializerSettings { 
    ReferenceLoopHandling = ReferenceLoopHandling.Ignore 
});

ReferenceLoopHandling.Ignore can prevent circular reference error.

answered May 19, 2016 at 11:45

Hamid Nasirloo

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1 Comment

renathy Over a year ago

I think this would prevent circular references, but would not prevent unnecesseraly loading related entities if not needed.

Marc Gravell · Accepted Answer · 2011-10-17 08:10:41Z

4

It sounds like EF is not giving you a ASSystem, but rather some subtle dynamic subclass of that with some EF goo. If that is correct, I would argue the simplest thing to do here is to use something like AutoMapper to get a non-EF copy (into a new ASSystem() instance, untouched by EF). However, a few alternatives:

you could try marking ASSystem as sealed, taking away EF's ability to inject itself
you you write a custom converter and register it - this is probably more work than mapping, though

answered Oct 17, 2011 at 8:10

Marc Gravell

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Comments

Massimo Zerbini · Accepted Answer · 2011-10-17 08:13:42Z

4

You can create a POCO object that can contains your data and can be serialized. For example define:

public class MySystem {
  public int SID {get; set;}
  public string Description {get; set;}
  public string SystemName {get; set;}
}

in your code use this statement:

IQuerable<MySystem> sysList = from s in ctx.AS_SYSTEM where s.SYSTEM_ID == query 
                           select new MySystem(){SID = s.SYSTEM_ID,  
                           Description = s.Description, SystemName = s.SystemName   };
MySystem sys = sysList.First();

Now you can serialize sys as in your example.

answered Oct 17, 2011 at 8:13

Massimo Zerbini

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2 Comments

Johan Over a year ago

Is there any way to make EF generate a class containing all the columns with the correct datatype as properties?

Massimo Zerbini Over a year ago

@Johan yes EF 4.0 supports POCO objects and EF 4.1 use POCO by default.

Rytis I · Accepted Answer · 2011-10-17 08:09:13Z

0

Not sure if this will help, but try to use DataContractJsonSerializer instead of JavaScriptSerializer. As far as I know DataContractJsonSerializer is prefered over JavaScriptSerializer.

answered Oct 17, 2011 at 8:09

Rytis I

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2 Comments

Johan Over a year ago

I forgot to mention that im using .net 3.5 and VS2008. I dont find it, and i suppose this is the problem? :)

Marc Gravell Over a year ago

I've generally found DataContractJsonSerializer gives somewhat... atypical JSON in a number of cases. I usually have more luck with JavaScriptSerializer or Json.NET

MarredCheese · Accepted Answer · 2019-08-29 19:16:15Z

-2

Try this; it works for me.

To return JSON data [in EF]:

Add reference System.Runtime.Serialization to the project.
Write code like below:

using System.Web.Script.Serialization;

    public string getValuesJson()
    {
        JavaScriptSerializer js = new JavaScriptSerializer();
        MyDBEntities ctx = new MyDBEntities();

        var myValues = (from m in ctx.TestEntity
                       where (m.id == 22)
                       select m).ToList();

        return js.Serialize(myValues);
    }

You can also check whether JSON string is valid at http://jsonlint.com/.

edited Aug 29, 2019 at 19:16

MarredCheese

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answered Apr 1, 2014 at 19:00

Muru Bakthavachalam

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