System.Text.Json.Serialization.JsonIgnoreAttribute not working in asp.net Core 3.1 partial ModelMetadataType class

[rocfatcat]

Describe the bug

The System.Text.Json.Serialization.JsonIgnoreAttribute not working as expected in partial class's
ModeMetaDataType class at ASP․NET Core 3.1.

To Reproduce

1. Setup demo project

git clone https://github.com/rocfatcat/JsonIgnoreTest.git
cd JsonIgnoreTest
dotnet run

2. Send HTTP GET request to the demo action

curl http://localhost:5000/api/Department

It return 500 status code and web application throw follow log message.

I expected api will return department data without instructor and course json data.

System.Text.Json.JsonException: A possible object cycle was detected which is not supported. This can either be due to a cycle or if the object depth is larger than the maximum allowed depth of 32.

For compare System.Text.Json.Serialization.JsonIgnoreAttribute and Newtonsoft.Json.JsonIgnoreAttribue result, i put Newtonsoft.Json example in Newtonsoft.Json_Test branch in the same git repository.

Here is the code snippet of the demo code:

Department.cs Content

    public partial class Department
    {
        public Department()
        {
            Course = new HashSet<Course>();
        }

        public int DepartmentId { get; set; }
        public string Name { get; set; }
        public decimal Budget { get; set; }
        public DateTime StartDate { get; set; }
        public int? InstructorId { get; set; }
        public byte[] RowVersion { get; set; }

        public virtual Person Instructor { get; set; }
        public virtual ICollection<Course> Course { get; set; }
    }

Department.Partial.cs

using System.Text.Json.Serialization;
using Microsoft.AspNetCore.Mvc;

...

    [ModelMetadataType(typeof(DepartmentModelMetadataType))]
    public partial class Department
    {
        ...
    }

    public partial class DepartmentModelMetadataType
    {
        [JsonIgnore]
        public virtual Person Instructor { get; set; }
        [JsonIgnore]
        public virtual ICollection<Course> Course { get; set; }
    }

Further technical details

• ASP.NET Core version: 3.1
• Include the output of dotnet --info: See below
• The IDE (VS / VS Code/ VS4Mac) you're running on, and it's version: VSCode 1.39.2

.NET Core SDK (reflecting any global.json):
 Version:   3.0.101
 Commit:    bc5f8df0f5

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.17134
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\3.0.101\

Host (useful for support):
  Version: 3.1.0
  Commit:  65f04fb6db

.NET Core SDKs installed:
  2.1.802 [C:\Program Files\dotnet\sdk]
  3.0.101 [C:\Program Files\dotnet\sdk]
  3.1.100 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.0.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.0.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.0.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

[mkArtakMSFT]

Thanks for contacting us. This looks like an issue on the CoreFx side. @pranavkm can you please look into this to confrim and move over, if so? Thanks!

[pranavkm]

@rocfatcat ModelMetadataType and other model binding specific types are used by MVC's model binding system. Models bound by deserializing the response body containing JSON or XML data are unaware of these types which would explain why you see this error. You would have to specify the JSON attributes on the model being bound.

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