How to deserialize a nested json string?

Question

Suppose I have this classes:

internal class Test
{
    public string value { get; set; }

    public Test(string value)
    {
        this.value = value;
    }
}

public class Response<T>
{
    private string errorMessage { get; }
    private T returnValue { get;  }

    public Response(string errorMessage, T returnValue)
    {
        this.errorMessage = errorMessage;
        this.returnValue = returnValue;
    }

    public bool HasError() { return errorMessage != ""; }

    public bool AssertEqualsReturnValue(object obj) { return returnValue.Equals(obj); }
        
}

and I have this Main function:

string json = 
@"{
    ""errorMessage"": ""This is an error"",
    ""returnValue"": {
        ""value"": ""this is what returns""
    }
}
";

Response<Test> r = JsonSerializer.Deserialize<Response<Test>>(json); ;
Console.WriteLine(r.AssertEqualsReturnValue("this is what returns"));
Console.WriteLine(r.HasError());

I get the next error message:

System.InvalidOperationException: 'Each parameter in the deserialization constructor on type 'IntroSE.Kanban.Backend.Response`1[ConsoleApp1.Test]' must bind to an object property or field on deserialization. Each parameter name must match with a property or field on the object. The match can be case-insensitive.'

It won't desirialize because I need to somehow tell the JsonSerializer I have a Test object in returnValue key. I saw some solutions online but the problem is they all use JsonConverter which is no in use anymore in .Net 6.0.

Have you tried to decorate your `Response` class's constructor with the [`JsonConstructor` attribute](https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-immutability?pivots=dotnet-6-0)? And the same should be applied for `Test`'s ctor. — Peter Csala, Apr 26 '22 at 10:31
Does it throw some exception? Or the deserialized value is null? Or ?? — Peter Csala, Apr 26 '22 at 10:37
@PeterCsala I have added the error message to the question body now, it says the keys do not much but they clearly do — D4NieLDev, Apr 26 '22 at 10:39
You receive that exception because `errorMessage` and `returnValue` are declared as `private`. — Peter Csala, Apr 26 '22 at 10:50
@PeterCsala I got the idea but I think it will benefit others :) — D4NieLDev, Apr 26 '22 at 10:57

score 1 · Accepted Answer · answered Apr 26 '22 at 11:03

You have defined your errorMessage and returnValue properties with private visibility. If you change them to public after that the exception will not be thrown.

Please be aware that the JsonInclude attribute can be used only in case of non-public property accessors, like private set; or private get;.

score 1 · Answer 2 · answered Apr 26 '22 at 11:09

1

FYI you can do this in VS

copy the json

{ "errorMessage": "This is an error", "returnValue": { "value": "this is what returns" } }
Choose EDIT < Paste Special > Paste JSON As Classes
Check and compare with your classes

answered Apr 26 '22 at 11:09

user3682728

467
3
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How to deserialize a nested json string?

2 Answers2