I'm writing an app that gets a Json
list of objects like this:
[
{
"ObjectType": "apple",
"ObjectSize": 35,
"ObjectCost": 4,
"ObjectTaste": "good",
"ObjectColor": "golden"
},
{
"ObjectType": "books",
"ObjectSize": 53,
"ObjectCost": 7,
"Pages": 100
},
{
"ObjectType": "melon",
"ObjectSize": 35,
"ObjectTaste": "good",
"ObjectCost": 5
},
{
"ObjectType": "apple",
"ObjectSize": 29,
"ObjectCost": 8,
"ObjectTaste": "almost good",
"ObjectColor": "red"
}
]
I want to make a base class ItemToSell
(size,cost), and derive Apple, Melon and Book from it, then make the deserialization based on the " ObjectType
" field to whatever class it fits. I want it to build a list of ItemToSell
objects, every object being Apple, Melon or Book.
How could I do this in .Net?
Thanks in advance :)
EDIT: I know how to deserialize it in a Big class with all the fields it can ever contain, like: Base(ObjectType,ObjectSize,ObjectCost,ObjectColor,Pages)
. But I want it to distinguish between classes by the ObjectType
so I won't have any usefulness fields like Pages field for every book item or ObjectTaste
for every book.
Some time ago I had the same problem.
You'll can use Json.NET, but if you don't have control over the json document (as in: 'it has been serialized by some other framework') you'll need to create a custom JsonConverter like this:
class MyItemConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
return typeof(ItemToSell).IsAssignableFrom(objectType);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
JObject obj = JObject.Load(reader);
string discriminator = (string)obj["ObjectType"];
ItemToSell item;
switch (discriminator)
{
case "apple":
item = new Apple();
break;
case "books":
item = new Books();
break;
case "melon":
item = new Melon();
break;
default:
throw new NotImplementedException();
}
serializer.Populate(obj.CreateReader(), item);
return item;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
}
}
Then you'll need to add it to the converters of the JsonSerializerSettings like so:
JsonSerializerSettings settings = new JsonSerializerSettings
{
TypeNameHandling = TypeNameHandling.Objects,
};
settings.Converters.Add(new MyItemConverter());
var items = JsonConvert.DeserializeObject<List<ItemToSell>>(response, settings);
You can use a CustomCreationConverter . This lets you hook into the deserialization process.
public abstract class Base
{
public string Type { get; set; }
}
class Foo : Base
{
public string FooProperty { get; set; }
}
class Bar : Base
{
public string BarProperty { get; set; }
}
class CustomSerializableConverter : CustomCreationConverter<Base>
{
public override Base Create(Type objectType)
{
throw new NotImplementedException();
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var jObject = JObject.Load(reader);
var type = (string)jObject.Property("Type");
Base target;
switch (type)
{
case "Foo":
target = new Foo();
break;
case "Bar":
target = new Bar();
break;
default:
throw new InvalidOperationException();
}
serializer.Populate(jObject.CreateReader(), target);
return target;
}
}
class Program
{
static void Main(string[] args)
{
var json = "[{Type:\"Foo\",FooProperty:\"A\"},{Type:\"Bar\",BarProperty:\"B\"}]";
List<Base> bases = JsonConvert.DeserializeObject<List<Base>>(json, new CustomSerializableConverter());
}
}
This is not an answer but in C# 6.0 you will be able to do this:
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Newtonsoft.Json.Linq;
[TestMethod]
public void JsonWithDollarOperatorStringIndexers()
{
// Additional data types eliminated for elucidation
string jsonText = @"
{
'Byte': {
'Keyword': 'byte',
'DotNetClassName': 'Byte',
'Description': 'Unsigned integer',
'Width': '8',
'Range': '0 to 255'
},
'Boolean': {
'Keyword': 'bool',
'DotNetClassName': 'Boolean',
'Description': 'Logical Boolean type',
'Width': '8',
'Range': 'True or false.'
},
}";
JObject jObject = JObject.Parse(jsonText);
Assert.AreEqual("bool", jObject.$Boolean.$Keyword);
}
Taken from here.
Define base class and derived classes.
the use [JSON.net](also available via NuGet) 1 to deserialize them.
Ie
class ItemToSell {
string Type {get;set;}
string Size {get;set;}
string Cost {get;set;}
}
class Book : ItemToSell { ...}
Then deserialize using
var catalog = JsonConvert.Deserialize<List<ItemToSell>>(json);
The deserializer will ignore unexpected properties. Call it again using a specific type to get other properties if you need.
your class:
public class RootObject
{
public string ObjectType { get; set; }
public int ObjectSize { get; set; }
public int ObjectCost { get; set; }
public string ObjectTaste { get; set; }
public string ObjectColor { get; set; }
public int? Pages { get; set; }
}
Deserialize using NewtonSoft JSON library like this:
var Jsonobject = JsonConvert.DeserializeObject<RootObject>(json);
Take a look at newtonsoft's JSON library
With it you can do stuff like:
...
public class Movie
{
public string Name;
public DateTime ReleaseDate;
public string[] Genres;
}
......
string json = @"{
'Name': 'Bad Boys',
'ReleaseDate': '1995-4-7T00:00:00',
'Genres': [
'Action',
'Comedy'
]
}";
Movie m = JsonConvert.DeserializeObject<Movie>(json);
string name = m.Name;
// Bad Boys
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