json - 我如何做 JSON 序列化程序忽略导航属性？

Question

我和这个问题完全一样:
How do I make JSON.NET ignore object relationships?

我看到了建议的解决方案，我知道我必须使用 Contract Revolver，我也看到了 Contract Resolver 的代码，但我不知道如何使用它。

我应该在 WebApiConfig.vb 中使用它吗？

我应该修改我的实体模型吗？

Answer 1

这是一个有用的问题👍，我希望这会有所帮助:
一种)
如果您手动创建了模型(没有 Entity Framework )，将关系属性标记为 virtual第一的。
如果您的模型是由 EF 创建的, 它已经为您和每个人做到了Relation Property标记为 virtual ，如下图所示:

Sample class:

public class PC
{
    public int FileFolderId {get;set;}

    public virtual ICollection<string> Libs { get; set; }
    public virtual ICollection<string> Books { get; set; }
    public virtual ICollection<string> Files { get; set; }
}

乙)
这些关系属性现在可以被 JSON 忽略。序列化程序使用以下 ContractResolver为 JSON.NET :
CustomResolver:

class CustomResolver : DefaultContractResolver
{
    private readonly List<string> _namesOfVirtualPropsToKeep=new List<string>(new String[]{});

    public CustomResolver(){}

    public CustomResolver(IEnumerable<string> namesOfVirtualPropsToKeep)
    {
        this._namesOfVirtualPropsToKeep = namesOfVirtualPropsToKeep.Select(x=>x.ToLower()).ToList();
    }

    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        JsonProperty prop = base.CreateProperty(member, memberSerialization);
        var propInfo = member as PropertyInfo;
        if (propInfo != null)
        {
            if (propInfo.GetMethod.IsVirtual && !propInfo.GetMethod.IsFinal
                && !_namesOfVirtualPropsToKeep.Contains(propInfo.Name.ToLower()))
            {
                prop.ShouldSerialize = obj => false;
            }
        }
        return prop;
    }
}

C)
最后 , 要轻松地序列化您的模型，请使用上述 ContractResolver .像这样设置:

// -------------------------------------------------------------------
// Serializer settings
JsonSerializerSettings settings = new JsonSerializerSettings
{
    // ContractResolver = new CustomResolver();
    // OR:
    ContractResolver = new CustomResolver(new []
    {
        nameof(PC.Libs), // keep Libs property among virtual properties
        nameof(PC.Files) // keep Files property among virtual properties
    }),
    PreserveReferencesHandling = PreserveReferencesHandling.None,
    ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
    Formatting = Formatting.Indented
};

// -------------------------------------------------------------------
// Do the serialization and output to the console
var json = JsonConvert.SerializeObject(new PC(), settings);
Console.WriteLine(json);

// -------------------------------------------------------------------
// We can see that "Books" filed is ignored in the output:
// {
//  "FileFolderId": 0,
//  "Libs": null,
//  "Files": null
// }

现在 ，所有导航(关系)属性 [ virtual properties] 将被自动忽略，除非您通过在代码中确定它们来保留其中一些。😎
Live DEMO

感谢来自 @BrianRogers他的回答 here .