自定义Odata格式化程序返回完整数据库而不是资源

Question

我使用自定义格式化程序将结果直接嵌入<script>标记中。格式化程序只是添加一个变量并序列化该实体。这是我的自定义格式化程序的简化实现：

        public override Task WriteToStreamAsync(Type type, object value, Stream writeStream, System.Net.Http.HttpContent content, System.Net.TransportContext transportContext)
        {
            return Task.Factory.StartNew(() =>
            {
                using (StreamWriter sw = new StreamWriter(writeStream))
                {
                    var jsonOutput = JsonConvert.SerializeObject(value, Newtonsoft.Json.Formatting.Indented, new JsonSerializerSettings
                    {
                        ReferenceLoopHandling = ReferenceLoopHandling.Ignore
                    });

                    sw.Write("var values=" + jsonOutput + ";");
                }

            });
        }

如果我使用$filter，$select或$expand请求资源，这样可以正常工作，但如果我只查询资源本身（例如http://localhost:53662/Categories?$format=jsone）则不行。然而，格式化程序序列化整个数据库。

以下是http://localhost:53662/Categories?$format=jsone的错误结果（正如您所看到的，它还会返回产品和标签，但不包含在Odata请求中）：

这是一个正确的例子，如果我添加一个Odata查询（这里是http://localhost:53662/Categories?$format=jsone&$select=Name）：

这是没有自定义格式化程序（http://localhost:53662/Categories）的正确结果：

Web API Controller非常简单：

        [EnableQuery]
        public IQueryable<Categories> Get(ODataQueryOptions<Categories> qOptions)
        {
            IQueryable<Categories> result = db.Categories;
            return result;
        }

        [EnableQuery]
        public SingleResult<Categories> Get([FromODataUri] int key, ODataQueryOptions<Categories> qOptions)
        {
            IQueryable<Categories> result = db.Categories.Where(x => x.Id == key);
            return SingleResult.Create(result);
        }

为什么自定义格式化程序返回完整数据库而不仅仅是请求的资源？

Answer 1

Well, I'm using Web API with ASP.MVC 4. You're using Web API 2, but it's kind of the same problem

In case you don't need that reference depth at all: add to your reference list, contained in codefirst model, new attribute [JsonIgnore]

Example:

public class Subgroup
{
    public int SubgroupId { get; set; }
    public string SubgroupName { get; set; }
    //relations
    public int GroupId { get; set; }
    public Group Group { get; set; }
}

public class Group
{
    public int GroupId { get; set; }
    public string GroupName { get; set; }
    //relations
    [JsonIgnore]
    public virtual List<Subgroup> Subgroups { get; set; } 
}

or you can just make it private (non-virtual).

In case you want to set up return result, try to work with DataContract attribute.

But we want to have a choice. Make it configurable (with own formatters). And documentation doesn't give proper answer. JsonFormatter.SerializerSettings.MaxDepth and JsonFormatter.MaxDepth do nothing. But no harm in trying:

var jsonOutput = JsonConvert.SerializeObject(value, Newtonsoft.Json.Formatting.Indented, new JsonSerializerSettings
{
   ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
   MaxDepth = 1
});

What else can I suggest: you can write your own formatter using JavaScriptSerializer