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!

与Json。网

 public class Movie
 {
            public string Name { get; set; }
            public string Description { get; set; }
            public string Classification { get; set; }
            public string Studio { get; set; }
            public DateTime? ReleaseDate { get; set; }
            public List<string> ReleaseCountries { get; set; }
 }

 Movie movie = new Movie();
 movie.Name = "Bad Boys III";
 movie.Description = "It's no Bad Boys";

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

结果将是:

{
   "Name": "Bad Boys III",
   "Description": "It's no Bad Boys"
 }

正如James Newton King所述:如果你自己创建序列化器，而不是使用JavaScriptConvert，那么你可以将NullValueHandling属性设置为忽略。

下面是一个例子:

JsonSerializer _jsonWriter = new JsonSerializer {
                                 NullValueHandling = NullValueHandling.Ignore
                             };

或者，按照@amit的建议

JsonConvert.SerializeObject(myObject, 
                            Newtonsoft.Json.Formatting.None, 
                            new JsonSerializerSettings { 
                                NullValueHandling = NullValueHandling.Ignore
                            });

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 );

.Net 6 - 在Program.cs中添加代码。这将忽略类或记录属性，如果它是空的。

using System.Text.Json.Serialization;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllers()
.AddJsonOptions(opts =>
{
    var enumConverter = new JsonStringEnumConverter();
    opts.JsonSerializerOptions.Converters.Add(enumConverter);
    opts.JsonSerializerOptions.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingDefault | JsonIgnoreCondition.WhenWritingNull;
});