使用 JSON.NET 序列化对象时如何添加自定义根节点?

问题描述

我为我的一些对象添加了一个自定义属性，如下所示:

I have added a custom property to some of my objects like this:

[JsonCustomRoot("status")]
public class StatusDTO 
{
    public int StatusId { get; set; }
    public string Name { get; set; }
    public DateTime Created { get; set; }
}

属性很简单:

public class JsonCustomRoot :Attribute
{
    public string rootName { get; set; }

    public JsonCustomRoot(string rootName)
    {
        this.rootName = rootName;
    }
}

序列化对象实例时 JSON.NET 的默认输出如下:

The default output from JSON.NET when serializing an instance of an object is this:

{"StatusId":70,"Name":"Closed","Created":"2012-12-12T11:50:56.6207193Z"}

现在的问题是:如何使用自定义属性的值向 JSON 添加根节点，如下所示:

{status:{"StatusId":70,"Name":"Closed","Created":"2012-12-12T11:50:56.6207193Z"}}

我发现有几篇文章提到了 IContractResolver 界面，但我无法掌握如何操作.我的尝试包括这段未完成的代码:

I have found several articles mentioning the IContractResolver interface, but I cannot grasp how to do it. My attempts include this unfinished piece of code:

protected override JsonObjectContract CreateObjectContract(Type objectType)
{
    JsonObjectContract contract = base.CreateObjectContract(objectType);

    var info = objectType.GetCustomAttributes()
                   .SingleOrDefault(t => (Type)t.TypeId==typeof(JsonCustomRoot));
    if (info != null)
    {
        var myAttribute = (JsonCustomRoot)info;
        // How can i add myAttribute.rootName to the root from here?
        // Maybe some other method should be overrided instead?
    }

    return contract;
}

推荐答案

这是一个专门针对 Web API 的解决方案，我也在使用:RootFormatter.cs

Here's a solution specifically for Web API, which I am also using: RootFormatter.cs

我是根据 为 ASP.NET Web API 创建 JSONP 格式化程序.

我没有使用自定义属性，而是重用了 JsonObjectAttribute 的 Title 字段.这是一个使用代码:

Instead of using a custom attribute I am reusing Title field of JsonObjectAttribute. Here's a usage code:

using Newtonsoft.Json

[JsonObject(Title = "user")]
public class User
{
    public string mail { get; set; }
}

然后，将 RootFormatter 添加到您的 App_Start 并在 WebApiConfig 中注册如下:

Then, add RootFormatter to your App_Start and register it as follows in WebApiConfig:

GlobalConfiguration.Configuration.Formatters.Insert(0, new RootFormatter());

我能够获得类似于 WCF 的 WebMessageBodyStyle.Wrapped 的包装响应:

I was able to get a wrapped response similar to WCF's WebMessageBodyStyle.Wrapped:

{"user":{
  "mail": "foo@example.com"
}}

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