c# - 防止在 WebAPI OData v4 服务中发出空值

Question

我正在运行 WebAPI OData v4 服务，我不希望发出空值。例如，当我请求一个 User 对象时，将返回以下内容:

"value": [
{
  "FirstName": "John",
  "LastName": "Smith",
  "EmailAddress": "john@smith.com",
  "PasswordHash": null,
  "PhoneNumber": "11234567890",
  "Website": null,
  "Id": "dac9706a-8497-404c-bb5a-ca1024cf213b"
}

由于 PasswordHash 和 Website 字段为空，我希望它们不包含在输出中。我在应用程序的注册 block 中尝试了以下几行，但它们都不起作用:

config.Formatters.JsonFormatter.SerializerSettings = new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore };
config.Formatters.JsonFormatter.SerializerSettings.DefaultValueHandling = DefaultValueHandling.IgnoreAndPopulate;
config.Formatters.JsonFormatter.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;

下面是 Register 方法的全部内容。我正在使用 Newtonsoft Json 包来处理 JSON 序列化。

public static void Register(HttpConfiguration config)
    {
        // Web API configuration and services
        config.SuppressDefaultHostAuthentication();
        config.Filters.Add(new HostAuthenticationFilter(OAuthDefaults.AuthenticationType));

        // Web API routes
        config.MapHttpAttributeRoutes();

        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );

        config.Routes.MapHttpRoute(
            name: "UploadComplete",
            routeTemplate: "UploadFiles/Complete",
            defaults: new { controller = "UploadFiles", action = "Complete" }
        );

        var builder = new ODataConventionModelBuilder();

        builder.EntitySet<Address>("Addresses");
        builder.EntitySet<Assignment>("Assignments");
        builder.EntitySet<Course>("Courses");
        builder.EntitySet<File>("Files");
        builder.EntitySet<UploadFile>("UploadFiles");
        builder.EntitySet<Organization>("Organizations");
        builder.EntitySet<Submission>("Submissions");
        builder.EntitySet<Term>("Terms");
        builder.EntitySet<User>("Users");

        config.MapODataServiceRoute(
            routeName: "ODataRoute",
            routePrefix: null,
            model: builder.GetEdmModel());

        // Neither of these lines work.
        config.Formatters.JsonFormatter.SerializerSettings = new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore };
        config.Formatters.JsonFormatter.SerializerSettings.DefaultValueHandling = DefaultValueHandling.IgnoreAndPopulate;
        config.Formatters.JsonFormatter.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;
    }

Answer 1

感谢 Brian Rogers 为我指明了正确的方向，我最终重写了 ODataEntityTypeSerializer，如下所示:

public override ODataEntry CreateEntry(SelectExpandNode selectExpandNode, EntityInstanceContext entityInstanceContext)
{
    ODataEntry entry = base.CreateEntry(selectExpandNode, entityInstanceContext);

    // Remove any properties which are null.
    List<ODataProperty> properties = new List<ODataProperty>();
    foreach (ODataProperty property in entry.Properties)
    {
        if (property.Value != null)
        {
            properties.Add(property);
        }
    }

    entry.Properties = properties;
    return entry;
}

然后我使用了来自 RaghuRam-Nadiminti's answer 的代码实现一个 CustomSerializerProvider 类，然后我可以在 Register 中使用它。