返回 Queryable 的 .Net WebApi OData 操作

Question

我想实现类似于以下所述的 RateProduct 操作：http://www.asp.net/web-api/overview/odata-support-in-aspnet-web-api/odata-actions

在该教程中，它被定义为：

[HttpPost]
public int RateProduct([FromODataUri] int key, ODataActionParameters parameters) 
{ 
    // ...
}

ODataModelBuilder modelBuilder = new ODataConventionModelBuilder();
modelBuilder.EntitySet<Product>("Products");

// New Code
ActionConfiguration rateProduct = modelBuilder.Entity<Product>().Action("RateProduct");
rateProduct.Parameter<int>("Rating");
rateProduct.Returns<int>();

但是，我有一个 Location 实体的用例，它足够聪明，可以返回它周围某个半径内的其他位置。大致应该是这样的：

[HttpPost]
public IQueryable<Location> GetLocationsWithinRadius([FromODataUri] int key, ODataActionParameters parameters) 
{ 
    // Get the Location instance intended to be the center of the radius by using the key
    // Do a radius search around it using (int)parameters["radius"] as the radius
    // return the IQueryable<Location> of all location found within that radius
}

ODataModelBuilder modelBuilder = new ODataConventionModelBuilder();
modelBuilder.EntitySet<Location>("Locations");

// New Code
ActionConfiguration getLocations = modelBuilder.Entity<Location>().Action("GetLocationsWithinRadius");
getLocations.Parameter<int>("radius");
getLocations.Returns<IQueryable<Location>>();

我很乐意让它工作，但当返回类型为 IQueryable<Location> 时，它目前不起作用。如果返回类型是像 int 这样的原始类型，那么它可以工作，否则当我在 fiddler 中创建帖子时会出现以下错误（帖子类似于http://localhost:2663/odata/Locations(2112)/GetLocationsWithinRadius，请求正文是{radius: 50}）：

{
  "odata.error":{
    "code":"","message":{
      "lang":"en-US","value":"An error has occurred."
    },"innererror":{
      "message":"The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; odata=minimalmetadata; streaming=true; charset=utf-8'.","type":"System.InvalidOperationException","stacktrace":"","internalexception":{
        "message":"The related entity set could not be found from the OData path. The related entity set is required to serialize the payload.","type":"System.Runtime.Serialization.SerializationException","stacktrace":"   at System.Web.Http.OData.Formatter.Serialization.ODataFeedSerializer.WriteObject(Object graph, ODataMessageWriter messageWriter, ODataSerializerContext writeContext)\r\n   at System.Web.Http.OData.Formatter.ODataMediaTypeFormatter.<>c__DisplayClassa.<WriteToStreamAsync>b__9()\r\n   at System.Threading.Tasks.TaskHelpers.RunSynchronously(Action action, CancellationToken token)"
      }
    }
  }
}

有可能做我想要完成的事情吗？如果是，我敢问返回的IQueryable<Location> 是否可以与 odata 参数组合...（那会很好）？

谢谢

Answer 1

您的操作配置似乎不正确。尝试以下方法，看看是否有效：

//getLocations.Returns<IQueryable<Location>>();
getLocations.ReturnsCollectionFromEntitySet<Location>("Locations");