Error – Object serialized to Object. JArray instance expected

Recently, I was involved in one of the migration projects. I had to migrate the existing ASP.NET Core 2.2-based project to .NET Core 3.1.

I faced a few challenges and errors during the migration. However, one of the errors related to JSON took a lot of my effort. So I thought to post it here.

Error message – Object serialized to Object. JArray instance expected

Below is the code snippet –

[HttpPost]
[Route("GetData")]
public IActionResult GetData([FromBody] object json)
{
    try
    {
        var jsonData = JSONModifier(JArray.FromObject(json));
        return Content(jsonData.ToString(), "application/json", Encoding.UTF8);
    }
    catch (Exception ex)
    {
        throw;
    }
}

public JArray JSONModifier(JArray inputJson)
{
    //Do some tasks here
    return inputJson;
}

The above code was working fine in ASP.NET Core 2.2. Once I migrated this application to .NET Core 3.1 then the above code started throwing the below error.

How to resolve this error – JArray instance expected

I started exploring the internet and tried one suggestion and it worked for me.

We need to make a small change that is mentioned below. Instead, JArray.FromObject we will use JArray.Parse and this way we will resolve this error.

var jsonData = JSONModifier(JArray.Parse(json.ToString()));

I hope this article is useful to you.

Please read the migration article – How to Migrate from ASP.NET Core 2.2 project to .NET Core 3.1?