I am trying to use Json.NET to serialize a subclass. The resulting json contains the serialized properties for the superclass but not the properties on the subclass object.
This seems to be related to an issue I found here on SO. But having to write a JsonConverter seems like overkill.
Sample subclass:
public class MySubclass : List<string>
{
public string Name { get; set; }
}
Sample of the serialization:
MySubclass myType = new MySubclass() { Name = "Awesome Subclass" };
myType.Add("I am an item in the list");
string json = JsonConvert.SerializeObject(myType, Newtonsoft.Json.Formatting.Indented);
Resulting json:
[
"I am an item in the list"
]
I expected to result to be more like this:
{
"Name": "Awesome Subclass",
"Items": [
"I am an item in the list"
]
}
Perhaps I am just not using the right configuration when serializing. Anyone have any suggestions?
According the documentation:
.NET lists (types that inherit from IEnumerable) and .NET arrays are
converted to JSON arrays. Because JSON arrays only support a range of
values and not properties, any additional properties and fields
declared on .NET collections are not serialized.
So, don't subclass List<T>, just add a second property.
public class MyClass
{
public List<string> Items { get; set; }
public string Name { get; set; }
public MyClass() { Items = new List<string>(); }
}
Here are my thoughts on this. I would think that your expected results would be more consistent with a class like this:
public class MyClass
{
public string Name { get; set; }
public List<string> Items { get; set; }
}
I would not expect to see an Items element in the serialized result for MySubclass : List<string> since there is no Items property on List nor on MySubclass.
Since your class MySubclass is actually a list of strings, I would guess (and I am just guessing here) that the SerializeObject method is merely iterating through your object and serializing a list of strings.
Related
I have some JSON:
{
"foo" : [
{ "bar" : "baz" },
{ "bar" : "qux" }
]
}
And I want to deserialize this into a collection. I have defined this class:
public class Foo
{
public string bar { get; set; }
}
However, the following code does not work:
JsonConvert.DeserializeObject<List<Foo>>(jsonString);
How can I deserialize my JSON?
That JSON is not a Foo JSON array. The code JsonConvert.DeserializeObject<T>(jsonString) will parse the JSON string from the root on up, and your type T must match that JSON structure exactly. The parser is not going to guess which JSON member is supposed to represent the List<Foo> you're looking for.
You need a root object, that represents the JSON from the root element.
You can easily let the classes to do that be generated from a sample JSON. To do this, copy your JSON and click Edit -> Paste Special -> Paste JSON As Classes in Visual Studio.
Alternatively, you could do the same on http://json2csharp.com, which generates more or less the same classes.
You'll see that the collection actually is one element deeper than expected:
public class Foo
{
public string bar { get; set; }
}
public class RootObject
{
public List<Foo> foo { get; set; }
}
Now you can deserialize the JSON from the root (and be sure to rename RootObject to something useful):
var rootObject = JsonConvert.DeserializeObject<RootObject>(jsonString);
And access the collection:
foreach (var foo in rootObject.foo)
{
// foo is a `Foo`
}
You can always rename properties to follow your casing convention and apply a JsonProperty attribute to them:
public class Foo
{
[JsonProperty("bar")]
public string Bar { get; set; }
}
Also make sure that the JSON contains enough sample data. The class parser will have to guess the appropriate C# type based on the contents found in the JSON.
I have some JSON:
{
"foo" : [
{ "bar" : "baz" },
{ "bar" : "qux" }
]
}
And I want to deserialize this into a collection. I have defined this class:
public class Foo
{
public string bar { get; set; }
}
However, the following code does not work:
JsonConvert.DeserializeObject<List<Foo>>(jsonString);
How can I deserialize my JSON?
That JSON is not a Foo JSON array. The code JsonConvert.DeserializeObject<T>(jsonString) will parse the JSON string from the root on up, and your type T must match that JSON structure exactly. The parser is not going to guess which JSON member is supposed to represent the List<Foo> you're looking for.
You need a root object, that represents the JSON from the root element.
You can easily let the classes to do that be generated from a sample JSON. To do this, copy your JSON and click Edit -> Paste Special -> Paste JSON As Classes in Visual Studio.
Alternatively, you could do the same on http://json2csharp.com, which generates more or less the same classes.
You'll see that the collection actually is one element deeper than expected:
public class Foo
{
public string bar { get; set; }
}
public class RootObject
{
public List<Foo> foo { get; set; }
}
Now you can deserialize the JSON from the root (and be sure to rename RootObject to something useful):
var rootObject = JsonConvert.DeserializeObject<RootObject>(jsonString);
And access the collection:
foreach (var foo in rootObject.foo)
{
// foo is a `Foo`
}
You can always rename properties to follow your casing convention and apply a JsonProperty attribute to them:
public class Foo
{
[JsonProperty("bar")]
public string Bar { get; set; }
}
Also make sure that the JSON contains enough sample data. The class parser will have to guess the appropriate C# type based on the contents found in the JSON.
I'm trying to consume data from a rest api.
I need to deserialize objects from a rest API using RestSharp.
The all objects in lists are an "object" element where the object's class is the value of a "type" attribute.
Here is an example of what I mean:
<list>
<object type="cat">
<id>107</id>
<name>Garry</name>
</object>
<object type="dog">
<id>83</id>
<name>Fluffy</name>
</object>
</list>
And partially implemented classes for the example:
public class Animal
{
public long Id { get; set; }
public string Name { get; set; }
}
[DeserializeAs(Name = "cat")]
public class Cat : Animal
{
}
[DeserializeAs(Name = "dog")]
public class Dog : Animal
{
}
It seems like the wrong way to go, but tried defining all of my classes using the attribute:
[DeserializeAs(Name = "object")]
This allows them to deserialize properly, as long as I know what type of object to expect in the list, and obviously the list only contains one type of object.
The problem comes in if I get a list containing different types of objects.
Is there a way to handle this well using the standard deserializer?
If not, I am open to ways to handle this effectively with a large number of different object types.
I looked at the standard deserializer. I am pretty sure it was not designed to handle this. I ended up making my own fork.
I added another attribute for describing the object in lists:
[DeserializeElementAs(Name = "", Attribute = "", Value = "")]
The attribute name might not be the best, but I was not sure what to call it.
So the classes for the xml from the question would be defined as:
public class Animal
{
public long Id { get; set; }
public string Name { get; set; }
}
[DeserializeElementAs(Name = "object", Attribute = "type", Value = "cat")]
[DeserializeAs(Name = "cat")]
public class Cat : Animal
{
}
[DeserializeElementAs(Name = "object", Attribute = "type", Value = "dog")]
[DeserializeAs(Name = "dog")]
public class Dog : Animal
{
}
I posted the code of fork to github if anyone else needs it.
https://github.com/comless/RestSharp/commit/1fea0fd97cadc7035dbea99c17b7423ca14b5267
I've just started to work with JSON and after having read a few articles, I'm still unclear if I'm looking at an array, list or just an object. It looks like this.
{
"list": [{
"fields": {
"id": "9222115557374550596",
...
},
},
{
"fields": {
"id": "9222115557374550597",
...
},
}],
"paging": {
"pageCurrent": 0,
"itemMin": 0,
"itemMax": 2,
"maxNextPages": 0,
"pageSize": 100
}
}
I'd like to deserialize it to be a list (or IEnumerable) of objects typed so that there's an Id property (perhaps not all fields have to be parsed in to the object).
When I try to do that using the following code:
List<Some> somes = JsonConvert.DeserializeObject<List<Some>>(dataAbove);
class Some { public String Id { get; set; } }
I get a long error message about me not being using the correct type and array and a bunch of other stuff that makes me confused. Am I on the right track or did I totally went off and got lost?!
I understand it's something with the list at the root. But what?! Or at least - what should I google for?!
Cannot deserialize the current JSON object (e.g. {\"name\":\"value\"}) into type 'System.Collections.Generic.List`1[ScriveProxy.Template]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly.\u000d\u000aTo fix this error either change the JSON to a JSON array (e.g. [1,2,3]) or change the deserialized type so that it is a normal .NET type (e.g. not a primitive type like integer, not a collection type like an array or List) that can be deserialized from a JSON object. JsonObjectAttribute can also be added to the type to force it to deserialize from a JSON object.\u000d\u000aPath 'list', line 1, position 8."
It can't be this one because the outer brackets are curly not squary...
In this solution, we end up with a single object, not an array, so it's not what I'm aiming for neither.
In your case, "list" is an array of "fields" objects.
"paging" is an object.
Both "list"` and "paging"` are in an un-named root object.
Working dotNetFiddle: https://dotnetfiddle.net/4qLTvq
See the output in the console pane of the fiddle above.
Here's How you should declare your Classes for Deserializing this particular JSON into C# Classes.
public class Fields
{
public string id { get; set; }
}
public class TheFields
{
public Fields fields { get; set; }
}
public class Paging
{
public int pageCurrent { get; set; }
public int itemMin { get; set; }
public int itemMax { get; set; }
public int maxNextPages { get; set; }
public int pageSize { get; set; }
}
public class RootObject
{
[Newtonsoft.Json.JsonPropertyAttribute("list")]
public List<TheFields> FieldsList { get; set; }
public Paging paging { get; set; }
}
And here's how you would deserialize the whole thing.
var rootObject = JsonConvert.DeserializeObject<RootObject>(jsonString);
Since List is a keyword, and to avoid confusion and collision, I changed it's Name to FieldsList and also renamed the List class to TheFields class. You may choose any other name(s) that you feel is appropriate.
Explanation on Object vs Array
An object is an unordered set of name/value pairs. An object begins with { (left brace) and ends with } (right brace). Each name is followed by : (colon) and the name/value pairs are separated by , (comma).
An array is an ordered collection of values. An array begins with [ (left bracket) and ends with ] (right bracket). Values are separated by , (comma).
Source: http://www.json.org/
If it starts with { it's an object.
If it starts with [ it's an array.
I'd like to serialize a class to XML, assigning an XML attribute to it. Snippet:
[XmlType(TypeName = "classmy")]
public class MyClass2 : List<object>
{
[XmlAttribute(AttributeName = "myattr")]
public string Name { get; set; }
}
public class MyConst
{
public MyConst()
{
MyClass2 myClass2 = new MyClass2 { 10, "abc" };
myClass2.Name = "nomm";
XmlSerializer serializer = new XmlSerializer(typeof(MyClass2));
serializer.Serialize(Console.Out, myClass2);
}
}
But the resulting XML looks like this
<?xml version="1.0" encoding="IBM437"?>
<classmy xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<anyType xsi:type="xsd:int">10</anyType>
<anyType xsi:type="xsd:string">abc</anyType>
</classmy>
All well and good, with the only exception being that myClass2.Name is not serialized. I was expecting something in the line of
<classmy myattr="nomm" [...]>[...]</classmy>
... Why isn't that serialized, and how can it be?
dont derive List<T>, create class with member List
[XmlType(TypeName = "classmy")]
public class MyClass2
{
[XmlAttribute(AttributeName = "Items")]
List<object> Items { get; set; } //need to change type in `<>`
[XmlAttribute(AttributeName = "myattr")]
public string Name { get; set; }
}
Alternative solution: use an array instead of a list and XmlElement
[XmlType(TypeName = "classmy")]
public class MyClass2
{
[XmlElement(ElementName = "Items")]
public object[] Items { get; set; }
[XmlAttribute(AttributeName = "myattr")]
public string Name { get; set; }
}
XmlSerializer treats List<> in special way:
XmlSerializer can process classes that implement IEnumerable or ICollection differently if they meet certain requirements. A class that implements IEnumerable must implement a public Add method that takes a single parameter. The Add method's parameter must be consistent (polymorphic) with the type returned from the IEnumerator.Current property returned from the GetEnumerator method. A class that implements ICollection in addition to IEnumerable (such as CollectionBase) must have a public Item indexed property (an indexer in C#) that takes an integer, and it must have a public Count property of type integer. The parameter passed to the Add method must be the same type as that returned from the Item property, or one of that type's bases. For classes implementing ICollection, values to be serialized will be retrieved from the indexed Item property rather than by calling GetEnumerator. Also note that public fields and properties will not be serialized, with the exception of public fields that return another collection class (one that implements ICollection). MSDN - scroll to XML Serialization Considerations
That why it serialized Your class as a list of objects only, without Your property. The best solution is to include List as class public property and mark it as XmlElement.