Dynamic retrieve json element .NET 6

Question

I want to retrieve a single value from a json string.

Previously I used Newtonsoft like this:

var jsonString = @"{ ""MyProp"" : 5 }";
dynamic obj = Newtonsoft.Json.Linq.JObject.Parse(jsonString);
        
Console.WriteLine(obj["MyProp"].ToString());

But I can't seem to get it to work in .NET 6:

I've tried this so far:

var jsonString = @"{ ""MyProp"" : 5 }";
dynamic obj = await System.Text.Json.JsonSerializer.Deserialize<dynamic>(jsonString);
        
Console.WriteLine(obj.MyProp.ToString());

which results in this error:

Unhandled exception. Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: The best overloaded method match for 'System.Text.Json.JsonElement.this[int]' has some invalid arguments

Oh, --- that is a good point... I have been asked "just to use the framework's one", hence my question, but indeed. — Stefan
– Stefan, Commented Dec 16, 2021 at 14:53

Stefan · Accepted Answer · 2022-08-04 08:59:17Z

5

Reading upon this github, I had success using this approach:

NET 6 will include the JsonNode type which can be used to serialize and deserialize dynamic data.

Trying it results in:

using System;
                    
public class Program
{
    public static void Main()
    {
        var jsonString = @"{ ""MyProp"" : 5 }";
        //parse it
        var myObject = System.Text.Json.JsonDocument.Parse(jsonString);
        //retrieve the value
        var myProp= myObject.RootElement
                            .GetProperty("MyProp");
        
        Console.WriteLine(myProp);
    }
}

Which seems to work in my case.

As by @robnick's comment - you can also chain GetProperty to get nested properties of the data structure.

var quote = rootElement.GetProperty("contents")
                       .GetProperty("quotes")[0]
                       .GetProperty("quote")
                       .GetString();

edited Aug 4, 2022 at 8:59

answered Dec 16, 2021 at 6:51

Stefan

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2 Comments

Stefan Over a year ago

Keep in mind, as nvoigt mentioned, you can still use NewtonSoft; for me this was just a project requirement.

robnick Over a year ago

You can also chain the .GetProperty() methods if you have nested JSON, example: .GetProperty("contents").GetProperty("quotes")[0].GetProperty("quote").GetString()

RobCole · Accepted Answer · 2023-03-13 17:41:43Z

2

Just in case someone else comes across this while searching on the subject...

If you parse as a JSON node directly, you can get your data in a single GetValue.

Example (using explicit types for clarity and '!' to handle nulls):

JsonNode? jnode = JsonNode.Parse(jsonString);
string quote = jnode["contents"]!["quotes"]!.AsArray()[0]!["quote"]!.GetValue<string>();

edited Mar 13, 2023 at 17:41

answered Mar 13, 2023 at 17:33

RobCole

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