我有一个模型，

public class Order
{
    public Guid Id { get; set; }
    public IEnumerable<string> ItemIds { get; set; }
    public string Currency { get; set; }
}

以及储存库，

public interface IOrderRepository
{
    IEnumerable<Order> Get();
    Order Get(Guid id);
    void Add(Order order);
    void Update(Guid id, Order order);
    // other irrelevant code has been deleted for simplicity
}

public class MemoryOrderRepository : IOrderRepository
{
    private readonly IList<Order> _orders = new List<Order>();
    public IEnumerable<Order> Get() => _orders;

    public Order Get(Guid id) => _orders.FirstOrDefault(o => o.Id == id);
    public void Add(Order order) => _orders.Add(order);

    public void Update(Guid id, Order order)
    {
        var target = _orders.FirstOrDefault(o => o.Id == id);
        if (target != null) target.ItemIds = order.ItemIds;
    }
    // other irrelevant code has been deleted for simplicity
}

已注册在Startup.cs中的数据类型，如下所示。

public void ConfigureServices(IServiceCollection services) =>
        services.AddSingleton<IOrderRepository, MemoryOrderRepository>()
                .AddControllers()
                .AddNewtonsoftJson();

其他相关的nuget软件包已经安装，如下所示。

<PackageReference Include="Microsoft.AspNetCore.JsonPatch" Version="3.1.1" />
<PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="3.1.1" />

测试控制器如下。

[Route("api/[controller]")]
[ApiController]
public class OrderController : ControllerBase
{
    private readonly IOrderRepository repo;

    public OrderController(IOrderRepository repo)
    {
        this.repo = repo;
    }

    [HttpGet]
    public IActionResult Get() => Ok(repo.Get());

    [HttpGet("{id:guid}")]
    public IActionResult Get(Guid id) => Ok(repo.Get(id));

    [HttpPost]
    public IActionResult Post(Order order)
    {
        Order target = new Order()
        {
            Id = Guid.NewGuid(),
            ItemIds = order.ItemIds
        };

        repo.Add(target);

        return CreatedAtAction(nameof(Get), new { id = target.Id }, null);
    }

    [HttpPatch("{id:guid}")]
    public IActionResult Patch(Guid id, JsonPatchDocument<Order> order)
    {
        Order target = repo.Get(id);
        if (target == null)
            return NotFound(new { Message = $"Item with id {id} does not exist." });

        order.ApplyTo(target);
        repo.Update(id, target);
        return Ok();
    }

    // other irrelevant code is deleted for simplicity
}

使用Postman，我成功地创建了一个新的订单，首先向服务器发送POST动词，然后通过发送GET动词来确认结果，如下所示。

问题

我尝试使用以下内容部分更新订单，但失败。

错误消息为
JSON修补程序文档格式错误，无法对其进行语法分析。
什么是错误的，如何修复它？
代替

{
    "ItemIds": ["xyz","123"]
}

我也试过

{
    "op":"replace",
    "path":"/ItemIds",
    "value": ["xyz","123"]
}

两者都不帮忙。