How to deserialize an anonymous object using C# System.Text.Json and access its properties?

Question

I have the following code:

var model = new
{
    Name = "Alexander"
};

var serializedModel = JsonSerializer.Serialize(model);
var deserializedModel = JsonSerializer.Deserialize<object>(serializedModel);
var name = deserializedModel!.GetType().GetProperty("Name");

The name variable is null as the "Name" property doesn't seem to exist. I do not have the model object when deserializing but just the JSON string.

I have tried using JsonConvert.DeserializeObject(serializedModel) from Newtonsoft and that seems to be working fine. However, I want to use System.Text.Json. Also, I have to use .GetType().GetProperty(...) as it's done like that in the external library I'm passing the deserialized object to.

Answer 1

JsonSerializer.Deserialize<object>(serializedModel) is equivalent to var JsonSerializer.Deserialize<JsonElement>(serializedModel); so depending on your requirements you can use it:

var deserializedModel = JsonSerializer.Deserialize<JsonElement>(serializedModel);
if (deserializedModel.TryGetProperty("Name", out var nameP))
{
    Console.WriteLine(nameP.ToString());
}

For experimentation purposes you can use non-generic method and provide Type instance (doubtful that it will be useful in real app):

var deserializedModel = JsonSerializer.Deserialize(serializedModel, model.GetType());

But usually it is better to stick to standard approach and just create class to use for deserialization. I.e.

class MyClass
{
    public string Name { get; set; }
}

var x = JsonSerializer.Deserialize<MyClass>(serializedModel);

Also you can look in other ways to perform dynamic deserialization via System.Text.Json (including JsonNode and JsonDocument APIs)

Answer 2

you need only one line of code

string name = (string) JsonObject.Parse(serializedModel).AsObject()["Name"]; //"Alexander"

UPDATE

But if you want it the ridiculous way , IMHO this it is

var deserializedModel = JsonSerializer.Deserialize<object>(serializedModel);

string name = ((JsonElement)deserializedModel).GetProperty("Name").GetString();

I am sorry but I will never understand why it is working this way. When I am working with text.json I just try to do everything the most akward way, inside out, and it is usully helps. You have to ask a text.json team how they are doing this kind of libraries.

just to compare using newtonsoft and text.json

//using Newtonsoft.Json;
string name = (string) JObject.FromObject(model)["Name"];

//using System.Text.Json;
var serializedModel = JsonSerializer.Serialize(model);
string name = JsonSerializer.Deserialize<JsonElement>(serializedModel)
                                      .GetProperty("Name").GetString();

Answer 3

You may not know the "original" type that led to the JSON. But if you know something about the shape (such as "it always has a string property called Name") there's nothing stopping you from deserializing to a type that matches that shape. For example:

using System;
using System.Text.Json;
                    
public class Program
{
    public static void Main()
    {
        var model = new
        {
            Name = "Alexander"
        };
        
        var serializedModel = JsonSerializer.Serialize(model);
        
        var deserializedModel = JsonSerializer.Deserialize<HasName>(serializedModel);
        SomeExternalLib.Foo(deserializedModel);         
    }
}

class SomeExternalLib
{
    public static void Foo(object o)
    {
        var nameProperty = o.GetType().GetProperty("Name");
        var name = nameProperty.GetValue(o);
        Console.WriteLine("I got the name: " + name);
    }
}

class HasName
{
    public string Name { get; set; }
}

Runnable in this fiddle.

Answer 4

After spending some time on the original issue I was able to get it running using Reflection.Emit and that might actually be the only way to achieve what I originally asked for as you have the properties from the JSON and you have to generate a class at runtime that has said properties.

A more detailed answer can be found here: https://stackoverflow.com/a/29428640

If you don't actually need something so complex then you can try to deserialize to ExpandoObject.