返回具有导航属性的ef核心对象时，控制器崩溃

Question

我的环境是Asp.Net Core 2.1 EF Core 2.1

public class Customer
{
    public int Id { get; set; }

    public string name { get; set; }
    public virtual ICollection<CustomerLocation> CustomerLocations { get; set; }


public class CustomerLocation
{
    public int Id { get; set; }
    public int customerId { get; set; }
    public string streetAddress { get; set; }
    public string zipCode { get; set; }
    public string city { get; set; }
    public string state { get; set; }
    public string category { get; set; }
    public virtual Customer Customer { get; set; }
}

在我的Api控制器中

    // GET: api/Customers
    [HttpGet]
    public IEnumerable<Customer> GetCustomers()
    {
        var custlist = _context.Customers
            .Include(c=>c.CustomerLocations)
            .ToList();

        return custlist;

    }

我想收到这个JSON

[
{
    id: 1,
    name: "My First Company",
    customerLocations: [
    {
        id: 1,
        customerId: 1,
        streetAddress: "13 Union Street",
        zipCode: "94111",
        city: "San Francisco",
        state: "CA",
        category: "Headquarter",
        customer: null
    },
    {
        id: 2,
        customerId: 1,
        streetAddress: "1098 Harrison St",
        zipCode: "94103",
        city: "San Francisco",
        state: "CA",
        category: "Warehouse",
        customer: null
    }]
},
{
    id: 2,
    name: "Another Company",
    customerLocations: [ ]
}
]

但我收到的答案是

[
{
    id: 1,
    name: "My First Company",
    customerLocations: [
    {
        id: 1,
        customerId: 1,
        streetAddress: "13 Union Street",
        zipCode: "94111",
        city: "San Francisco",
        state: "CA",
        category: "Headquarter"

然后尝试进入“ customerLocation”的“ customer”导航属性会崩溃。

我发现摆脱这种情况的唯一方法是在每个CustomerLocation中显式将所有“客户”引用无效，但是我不认为这是处理此问题的正确方法。

Answer 1

发生此错误的原因是在序列化Customer引用循环，并且如您将客户引用设置为null时所说的那样，避免了引用循环。

处理它的另一种方法是在startup.cs为Json序列化程序设置ReferenceLoopHandling

services
    .AddMvc()
    .AddJsonOptions(config =>
    {
        config.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
    });