.NET 10 binding an IEnumerable record entries missing when nullable parameters are null

[norr-carr]

Description

We have Web Application with configuration supplied by an appsettings.json file. The configuration includes a collection of a custom type with nullable values. Prior to upgrading to .NET 10, the collection included instances with null entries in the nullable fields. After upgrading to .NET 10, any entry with a null field is missing from the collection.

Reproduction Steps

I created a basic Web Application in Visual Studio. The Program.cs includes:

var builder = WebApplication.CreateBuilder(args);

var options = builder.Configuration.GetSection("CustomOptions").Get<Options>();

builder.Services.AddControllers();

var app = builder.Build();

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

public record Options
{
  public string? EnableFeatureX { get; init; }
  public IEnumerable<User> Users { get; init; } = [];
}

public record User
(
  int Id,
 string? Name
);

and the appsettings file includes:

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*",
  "CustomOptions": {
    "EnableFeatureX": null,
    "Users": [
      {
        "Id": 1,
        "Name": "Noah"
      },
      {
         "Id": 2,
        "Name": null
      }
    ]
  }
}

Expected behavior

I expect to see that the "options" object when run has two entries in the Users ienumerable, one with Id: 1, Name: "Noah" and one with Id: 2, Name: null

Actual behavior

The "options" object only has one entry, Id: 1, Name: "Noah"

Regression?

This works as I expect in .NET 9. It does not work in .NET 10.

Known Workarounds

If you change the definition of "User" from a Constructor based record to one with explicit properties, expected behavior is restored:

public record User
{
  public int Id { get; init; }
 public string? Name { get; init; }
}

Configuration

net10.0
Visual Studio 26 (18.2)
Windows 11

Other information

.NET Fiddle .NET 9 https://dotnetfiddle.net/4bYI7v
.NET 10 https://dotnetfiddle.net/2vLnXU