Which Json deserializer provides IList <T> collections?
I am trying to deserialize json for an object model where collections are represented as IList<T>
types.
The actual deserialization is here:
JavaScriptSerializer serializer = new JavaScriptSerializer();
return serializer.Deserialize<IList<Contact>>(
(new StreamReader(General.GetEmbeddedFile("Contacts.json")).ReadToEnd()));
Before I post the exception I'm getting, you should know what implicit conversions are. This is the type Contact
:
public class Contact
{
public int ID { get; set; }
public string Name { get; set; }
public LazyList<ContactDetail> Details { get; set; }
//public List<ContactDetail> Details { get; set; }
}
And this is the type ContactDetail
:
public class ContactDetail
{
public int ID { get; set; }
public int OrderIndex { get; set; }
public string Name { get; set; }
public string Value { get; set; }
}
It is important to know with LazyList<T>
what it implements IList<T>
:
public class LazyList<T> : IList<T>
{
private IQueryable<T> _query = null;
private IList<T> _inner = null;
private int? _iqueryableCountCache = null;
public LazyList()
{
this._inner = new List<T>();
}
public LazyList(IList<T> inner)
{
this._inner = inner;
}
public LazyList(IQueryable<T> query)
{
if (query == null)
throw new ArgumentNullException();
this._query = query;
}
Now this class definition LazyList<T>
was fine until I tried to deserialize the Json into it. Seems to System.Web.Script.Serialization.JavaScriptSerializer
serialize lists in List<T>
, which makes sense at this age, but I need them in a type IList<T>
, so they'll be injected into mine LazyList<T>
(at least where I think I'm going wrong).
I am getting this exception:
System.ArgumentException: Object of type 'System.Collections.Generic.List`1[ContactDetail]' cannot be converted to type 'LazyList`1[ContactDetail]'..
When I try to use List<ContactDetail>
in my type Contact
(as you can see above) it works. But I don't want to use List<T>
. I even tried to inherit from the LazyList<T>
inheritance List<T>
, which seemed to work, but passing the List<T>
internal T[]
to my implementation was a nightmare and I just don't want the bells and whistles List<T>
anywhere in my model.
I have also tried some other json libraries to no avail (I may not be able to use them fully. I have replaced links more or less and tried to repeat the code at the beginning of this question. Maybe passing parameters to parameters will help?).
I don't know what to try now. Am I going with a different deserializer? Can I customize deserialization? Do I need to change my types to please the deserializer? Do I need to worry more about implicit casting, or just implement a different interface?
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I ended up using Json.NET lib which has good linq support for custom mapping. This is what ended up with my deserialization:
JArray json = JArray.Parse(
(new StreamReader(General.GetEmbeddedFile("Contacts.json")).ReadToEnd()));
IList<Contact> tempContacts = (from c in json
select new Contact
{
ID = (int)c["ID"],
Name = (string)c["Name"],
Details = new LazyList<ContactDetail>(
(
from cd in c["Details"]
select new ContactDetail
{
ID = (int)cd["ID"],
OrderIndex = (int)cd["OrderIndex"],
Name = (string)cd["Name"],
Value = (string)cd["Value"]
}
).AsQueryable()),
Updated = (DateTime)c["Updated"]
}).ToList<Contact>();
return tempContacts;
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Can't deserialize directly to an interface as interfaces are just a contract. The JavaScriptSerializer must deserialize to some concrete type that implements IList <T>, and the most logical choice is List <T>. You will have to convert the list to a LazyList, which should be fairly simple given the code you posted:
var list = serializer.Deserialize<IList<Contact>>(...);
var lazyList = new LazyList(list);
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Unfortunately, you probably need to fix your class as the deserializer doesn't know it should be of type IList, since List is an implementation of IList.
Since the deserializers at http://json.org have a source available, you can simply modify it to do what you want.
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