Issue with .NET Core 3.1

[Quatra]

Hello,

I've tried to use your code in .NET Core 3.1 but it was not working. I've received 400 Bad Request. I've found out that the Id was missing in the serialized object.

The fix is simple. In the AnnotationModel, I've changed public Guid Id = Guid.NewGuid(); to public Guid Id { get; set; } = Guid.NewGuid(); and it worked.

Of course, I've use the System.Text.Json.JsonSerializer class to serialize. It is different from the JavaScriptSerializer used in this repo.