.NET Core 3中未触发ShouldSerialize方法 [英] ShouldSerialize method is not triggered in .NET Core 3

问题描述

我通常使用ShouldSerialize来排除没有数据的属性，例如数组，但是现在，当我仅在.NET Core 3中使用JSON序列化程序时，它似乎不会被触发.使用NewtonSoft时已触发该事件，但由于不再需要它，因此已将其从项目中删除.

I normally use ShouldSerialize to exclude properties that have no data such as array but now, it does not appear to be triggered when I'm only using JSON serializer in .NET Core 3. It was being triggered when using NewtonSoft but I've removed it from my project since it no longer appears to be required.

例如:

    private ICollection<UserDto> _users;

    public ICollection<UserDto> Users
    {
        get => this._users ?? (this._users = new HashSet<UserDto>());
        set => this._users = value;
    }

    public bool ShouldSerializeUsers()
    {
        return this._users?.Count > 0;
    }

有什么想法为什么不应该触发ShouldSerializeUsers?

Any ideas why ShouldSerializeUsers is not being triggered?

我看到了其他可以使用的答案:

I've seen other answers where you can use:

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc()
        .AddJsonOptions(options => { 
        options.SerializerSettings.NullValueHandling = 
        NullValueHandling.Ignore;
    });
}

但是我想知道是否还有其他方法可以处理此问题，因为我没有使用.AddMvc

But I'd like to know if there is another way to handle this as I'm not using .AddMvc

谢谢.

推荐答案

在ASP.NET Core 3.0中未触发ShouldSerialize的原因是，在此版本和后续版本的ASP.NET中， a默认情况下，将使用不同的JSON序列化程序，即

The reason that your ShouldSerialize is not triggered in ASP.NET Core 3.0 is that, in this and subsequent versions of ASP.NET, a different JSON serializer is being used by default, namely System.Text.Json.JsonSerializer. See:

• 尝试新系统. Text.Json API .
• 在3.0#325中对Microsoft.AspNetCore.App进行了重大更改 .
• .NET Core 3.0#90中JSON的未来 .

不幸的是，从.NET Core 3.1开始，此序列化器不支持ShouldSerializeXXX()模式.如果这样做的话，它会在

Unfortunately as of .NET Core 3.1 this serializer does not support the ShouldSerializeXXX() pattern; if it did it would be somewhere in JsonSerializer.Write.HandleObject.cs -- but it's not. The following issues track requests for conditional serialization:

• .net core 3.0 system.text.json选项，用于忽略属性在运行时，例如newstonsoft DefaultContractResolver#42043 .

System.Text.Json选项可忽略序列化和安培中的默认值;反序列化#779 .

要恢复ShouldSerialize功能，您可以还原为使用Newtonsoft，如此答案所示为 .net Core 3.0中IMvcBuilder AddJsonOptions放在哪里? 通过添加基于Newtonsoft.Json的JSON格式支持 :

To restore ShouldSerialize functionality, you can revert back to using Newtonsoft as shown in this answer to Where did IMvcBuilder AddJsonOptions go in .Net Core 3.0? by poke, and also Add Newtonsoft.Json-based JSON format support:

1. 安装 Microsoft.AspNetCore.Mvc.NewtonsoftJson .

2. 然后在Startup.ConfigureServices中调用AddNewtonsoftJson():

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers()
        .AddNewtonsoftJson();
}

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