JSON SerializeObject fails to serialize class with abstract member on iOS hardware - xamarin.forms

Question

When I try to run my Xamarin Forms application on an actual iPhone, it fails with a System.MissingMethodException: "Constructor on type 'System.ComponentModel.ReferenceConverter' not found."
It works fine on the iOS Simulators as well as on Android hardware and virtual devices.
I've been able to narrow it down to the following scenario: serializing an object with an interface referenced member:
public class Widget {
public ISprocket Sprocket { get; set; };
}
public interface ISprocket {
int SprocketId { get; set; }
}
Executing the lines:
var w = new Widget { Sprocket = new Sprocket { SprocketId = 1 } };
string result = JsonConvert.SerializeObject(w);
works everywhere (seemingly) except on my iPhone 8+, where it throws a System.MissingMethodException
I'm using the most current versions of XF (2.5.0.122203) and JSON.NET (10.0.3).
To recreate this problem, create a new Xamarin Forms solution with an iOS client called "TestBed". Add Newtonsoft.Json via nuget, then create a page
"TestBedPage" with the following content:
using System;
using Newtonsoft.Json;
using Xamarin.Forms;
namespace TestBed
{
public class TestBedPage : ContentPage
{
public TestBedPage()
{
try
{
var m = new Widget { Sprocket = new Sprocket { SprocketId = 1 } };
var st = JsonConvert.SerializeObject(m);
Content = new Label { Text = st };
} catch (Exception ex) {
Content = new Label { Text = ex.ToString() };
}
}
}
public class Widget
{
public string Title { get; set; } = string.Empty;
public ISprocket Sprocket { get; set; }
}
public interface ISprocket
{
int SprocketId { get; set; }
}
public class Sprocket : ISprocket
{
public int SprocketId { get; set; }
}
}
Deploy it to an iPhone and run. You should get a screenful of MissingMethodException stack trace.
Does anyone have any idea what's going on here?

Answer 1

The issue is that something is trying to instantiate via Activator class an instance of System.ComponentModel.ReferenceConverter via its System.Type ctor but since it isn't referenced directly in you application it gets removed by the managed linker.
You need to provide a custom linker configuration file ,add it to your Xamarin.iOS project.
Refer to here