c# - WebAPI 暂时从 OnActionExecuted 覆盖 JsonFormatter

Question

我正在尝试创建一个属性，以不同方式序列化从操作返回的数据

public override void OnActionExecuted(HttpActionExecutedContext filterContext)
{
    var content = (filterContext.Response.Content as ObjectContent);

    if (content == null)
    {
        return;
    }

    if (content.ObjectType.IsGenericType 
        && content.ObjectType.GetGenericTypeDefinition() == typeof (Page<>))
    {
        var pageObject = (content.Value as IPage);
        var jsonFormatterRule = new JsonFormatterRule();
        var pageJson = JsonConvert.SerializeObject(pageObject.ItemsArray, 
                                                jsonFormatterRule.GetPascalCasedSettings());

       //How do I set the content that \/ doesn't compile?
       //filterContext.Response.Content = pageJson;
   }
}

这是 JsonFormatterRules，任何人都想看到它们。

public JsonSerializerSettings GetDefaultSettings()
{
    var settings = new JsonSerializerSettings()
    {
        Formatting = Formatting.Indented,
        ContractResolver = new CamelCasePropertyNamesContractResolver(),
        DateTimeZoneHandling = DateTimeZoneHandling.RoundtripKind,
    };

    settings.Converters.AddRange(defaultConfiguredConverters);
    return settings;
}

public JsonSerializerSettings GetPascalCasedSettings()
{
    var settings = this.GetDefaultSettings();
    settings.ContractResolver = new DefaultContractResolver();

    return settings;
}

如何设置 Action 执行时的内容？我无法将默认序列化器全局更改为 DefaultContract，因为它可能会出现线程问题。

另外，我不想创建新的响应并从旧的响应中复制 header ，这似乎太过分了。

Answer 1

实现此目的的一种方法是定义自定义格式化程序。

首先，定义你的属性:

[AttributeUsage(AttributeTargets.Class)]
public sealed class SpecialSerializeAttribute : Attribute
{
}

现在创建一个将找到属性的格式化程序:

public class SpecialSerializeFormatter : MediaTypeFormatter
{
    public SpecialSerializeFormatter()
    {
        //You can add any other supported types here.
        this.SupportedMediaTypes.Add(new MediaTypeHeaderValue("application/json"));
    }

    public override bool CanReadType(Type type)
    {
        //you can just return false if you don't want to read any differently than your default way
        //if you return true here, you should override the ReadFromStreamAsync method to do custom deserialize
        return type.IsDefined(typeof(SpecialSerializeAttribute), true));
    }

    public override bool CanWriteType(Type type)
    {
        return type.IsDefined(typeof(SpecialSerializeAttribute), true));
    }

    public override async Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content,
        TransportContext transportContext)
    {

        //value will be your object that you want to serialize

        //add any custom serialize settings here
        var json = JsonConvert.SerializeObject(value);

        //Use the right encoding for your application here
        var byteArray = Encoding.UTF8.GetBytes(json);
        await writeStream.WriteAsync(byteArray, 0, byteArray.Length);
    }
}

在您的 WebApiConfig.cs 中注册格式化程序

你也可以直接为每个类型构建一个格式化程序，然后你就不必做属性了。只需更改您的 CanRead 和 CanWrite 方法。我发现基于这些直接类型会得到更好的结果，因为它不是一个通用的格式化程序，您可能需要根据类型应用自定义逻辑，但上面的答案应该可以满足您的需求。