c# - 如何根据每个请求更改 JsonSerializerSettings

Question

我想为 DateTime 使用不同的格式关于查询字符串参数的字段:即如果查询字符串包含 dateFormat=iso参数，我想返回 ISO 6801 中的日期:

{
  "date": "2018-03-27T12:20:34.248563Z"
}

但是如果查询字符串包含dateFormat=unix参数，我想以 UNIX 时间返回日期:

{
  "date": 1522152517
}

使用 JsonResult 很容易实现和 ResultFilter :

public class DateFormatResultFilter : IAsyncResultFilter
{
    public async Task OnResultExecutionAsync(ResultExecutingContext context,ResultExecutionDelegate next)
    {
        var dateTimeFormat = context.HttpContext.Request.Query["dateFormat"].FirstOrDefault() ?? "iso8601";
        var converter = GetConverter(dateTimeFormat);

        var jsonSettings = context.HttpContext.RequestServices
            .GetRequiredService<IOptionsSnapshot<MvcJsonOptions>>()
            .Value.SerializerSettings;

        jsonSettings.Converters.Add(converter);

        if (context.Result is JsonResult jsonResult)
        {
            var value = jsonResult.Value;


            context.Result = new JsonResult(value, jsonSettings);
        }
        await next();
    }
}

我不想争夺全局JsonSerializerSettings , 所以我决定 IOptionsSnapshot<MvcJsonOptions>而不是 IOptions<MvcJsonOptions> .

但是我怎样才能为 ObjectResult 实现这种行为呢？ ？

Answer 1

至于 ObjectReault，您可以使用新的 JsonOutputFilter 和所需的 JsonSerializerSettings 创建一个新的 ObjectResult:

var jsonSerializationSettings = ...;
if (context.Result is ObjectResult objectResult)
{
    var result = new ObjectResult(objectResult.Value)
    {
        ContentTypes = objectResult.ContentTypes,
        DeclaredType = objectResult.DeclaredType,
        StatusCode = objectResult.StatusCode,
        Formatters = new FormatterCollection<IOutputFormatter>(objectResult.Formatters)
    };
    result.Formatters.RemoveType<JsonOutputFormatter>();
    result.Formatters.Add(new JsonOutputFormatter(jsonSerializationSettings, ArrayPool<char>.Shared));
    context.Result = result;
}