你可以写:[JsonProperty("property_name"，DefaultValueHandling = DefaultValueHandling. ignore)]

它还负责使用默认值(不仅仅是null)不序列化属性。例如，它对枚举很有用。

对于System.Text.Json和.NET Core 3.0，这对我来说是可行的:

var jsonSerializerOptions = new JsonSerializerOptions()
{
    IgnoreNullValues = true
};
var myJson = JsonSerializer.Serialize(myObject, jsonSerializerOptions );

或者像这样设置。

services.AddMvc().AddJsonOptions(options =>
  options.JsonSerializerOptions.IgnoreNullValues = true;
});

To expound slightly on GlennG's very helpful answer (translating the syntax from C# to VB.Net is not always "obvious") you can also decorate individual class properties to manage how null values are handled. If you do this don't use the global JsonSerializerSettings from GlennG's suggestion, otherwise it will override the individual decorations. This comes in handy if you want a null item to appear in the JSON so the consumer doesn't have to do any special handling. If, for example, the consumer needs to know an array of optional items is normally available, but is currently empty... The decoration in the property declaration looks like this:

<JsonPropertyAttribute("MyProperty", DefaultValueHandling:=NullValueHandling.Include)> Public Property MyProperty As New List(of String)

For those properties you don't want to have appear at all in the JSON change :=NullValueHandling.Include to :=NullValueHandling.Ignore. By the way - I've found that you can decorate a property for both XML and JSON serialization just fine (just put them right next to each other). This gives me the option to call the XML serializer in dotnet or the NewtonSoft serializer at will - both work side-by-side and my customers have the option to work with XML or JSON. This is slick as snot on a doorknob since I have customers that require both!

JSON。NET也尊重DataMemberAttribute上的EmitDefaultValue属性，以防你不想将newtonsoft特定的属性添加到你的模型中:

[DataMember(Name="property_name", EmitDefaultValue=false)]

可以在他们的网站(http://james.newtonking.com/archive/2009/10/23/efficient-json-with-json-net-reducing-serialized-json-size.aspx)上的这个链接中看到，我支持使用[Default()]来指定默认值

摘自链接

   public class Invoice
{
  public string Company { get; set; }
  public decimal Amount { get; set; }

  // false is default value of bool
  public bool Paid { get; set; }
  // null is default value of nullable
  public DateTime? PaidDate { get; set; }

  // customize default values
  [DefaultValue(30)]
  public int FollowUpDays { get; set; }
  [DefaultValue("")]
  public string FollowUpEmailAddress { get; set; }
}


Invoice invoice = new Invoice
{
  Company = "Acme Ltd.",
  Amount = 50.0m,
  Paid = false,
  FollowUpDays = 30,
  FollowUpEmailAddress = string.Empty,
  PaidDate = null
};

string included = JsonConvert.SerializeObject(invoice,
  Formatting.Indented,
  new JsonSerializerSettings { });

// {
//   "Company": "Acme Ltd.",
//   "Amount": 50.0,
//   "Paid": false,
//   "PaidDate": null,
//   "FollowUpDays": 30,
//   "FollowUpEmailAddress": ""
// }

string ignored = JsonConvert.SerializeObject(invoice,
  Formatting.Indented,
  new JsonSerializerSettings { DefaultValueHandling = DefaultValueHandling.Ignore });

// {
//   "Company": "Acme Ltd.",
//   "Amount": 50.0
// }