Adding JsonIgnoreAttribute to new property fails with ArgumentException

[liuliang-wt]

Description

using System.Text.Json;
using System.Text.Json.Serialization;

ClassB b = new ClassB();
var test = JsonSerializer.Serialize(b);
Console.ReadLine();

public class ClassA
{
    [JsonIgnore]
    public string test { get; set; }
}

public class ClassB : ClassA
{
    [JsonIgnore]
    public new string test { get; set; }
}

The above code will throw an exception: System.ArgumentException:“An item with the same key has already been added. Key: test”

When both base class and derived class has a property with the same name (derived class using new to override property in base class), and both of this two properties marked as [JsonIgnore], Serialize function throw this exception.

[ghost]

Tagging subscribers to this area: @dotnet/area-system-text-json, @gregsdennis
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

using System.Text.Json;
using System.Text.Json.Serialization;

ClassB b = new ClassB();
var test = JsonSerializer.Serialize(b);
Console.ReadLine();

public class ClassA
{
[JsonIgnore]
public string test { get; set; }
}

public class ClassB : ClassA
{
[JsonIgnore]
public new string test { get; set; }
}

The above code will throw an exception: System.ArgumentException:“An item with the same key has already been added. Key: test”

When both base class and derived class has a property with the same name (derived class using new to override property in base class), and both of this two properties marked as [JsonIgnore], Serialize function throw this exception.

Author:	liuliang-wt
Assignees:	-
Labels:	area-System.Text.Json
Milestone:	-

[eiriktsarpalis]

I can reproduce -- this belongs in the same class of bugs as #73255. This one is more interesting as it's actually failing with an exception during contract resolution.