asp.net Web API - Breeze webapi Controller 'cannot support querying' over DbSet error

Question

我的设置非常类似于微风样例应用程序，它来自样本nuget。这是我的api控制器的代码:

[JsonFormatter, ODataActionFilter]
public class WorkOrdersController : ApiController
{
    readonly EFContextProvider<WorkOrdersContext> _contextProvider =
        new EFContextProvider<WorkOrdersContext>();
    public WorkOrdersController()
    {
        // I was thinking this may be the cause of the issue
        this._contextProvider.Context.Configuration.ProxyCreationEnabled = false;
    }
    [HttpGet]
    public string Metadata()
    {
        return _contextProvider.Metadata();
    }
    [HttpPost]
    public SaveResult SaveChanges(JObject saveBundle)
    {
        return _contextProvider.SaveChanges(saveBundle);
    }
    [HttpGet]
    public IQueryable<WorkOrder> WorkOrders()
    {
        return _contextProvider.Context.WorkOrders;
    }
}

我遇到的问题是，当我尝试对WorkOrders操作执行查询时，我得到500 -内部服务器错误，这是响应的有效载荷:

{"$id":"1","$type":"System.Web.Http.HttpError, System.Web.Http","Message":"An error has occurred.","ExceptionMessage":"The action 'WorkOrders' on controller 'WorkOrders' with return type 'System.Collections.Generic.List`1[[WorkOrders.Domain.Models.WorkOrder, WorkOrders.Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]' cannot support querying. Ensure the type of the returned content is IEnumerable, IQueryable, or a generic form of either interface.","ExceptionType":"System.InvalidOperationException","StackTrace":"   at System.Web.Http.QueryableAttribute.ValidateReturnType(Type responseContentType, HttpActionDescriptor actionDescriptor)rn   at System.Web.Http.QueryableAttribute.OnActionExecuted(HttpActionExecutedContext actionExecutedContext)rn   at System.Web.Http.Tracing.ITraceWriterExtensions.TraceBeginEnd(ITraceWriter traceWriter, HttpRequestMessage request, String category, TraceLevel level, String operatorName, String operationName, Action`1 beginTrace, Action execute, Action`1 endTrace, Action`1 errorTrace)rn   at System.Web.Http.Tracing.Tracers.ActionFilterAttributeTracer.OnActionExecuted(HttpActionExecutedContext actionExecutedContext)rn   at System.Web.Http.Filters.ActionFilterAttribute.<>c__DisplayClass2.<System.Web.Http.Filters.IActionFilter.ExecuteActionFilterAsync>b__0(HttpResponseMessage response)rn   at System.Threading.Tasks.TaskHelpersExtensions.<>c__DisplayClass41`2.<Then>b__40(Task`1 t)rn   at System.Threading.Tasks.TaskHelpersExtensions.ThenImpl[TTask,TOuterResult](TTask task, Func`2 continuation, CancellationToken cancellationToken, Boolean runSynchronously)"}

WorkOrders is Dbset on context:

public DbSet<WorkOrder> WorkOrders { get; set; }

我也试过显式地将它转换为IQueryable，没有变化:

[HttpGet]
public IQueryable<WorkOrder> WorkOrders()
{
    return (IQueryable<WorkOrder>)_contextProvider.Context.WorkOrders;
}

对我来说唯一有效的方法是:

[HttpGet]public IEnumerable WorkOrders(){返回_contextProvider.Context.WorkOrders.AsEnumerable ();}

然而，这在客户端给我带来了另一个问题，如本问题所述。

Answer 1

这里只是猜测，但是您可以尝试使用带有以下属性的最新breeze (v 0.82.1)吗?

[BreezeController]

而不是这些

[JsonFormatter ODataActionFilter]

新的[BreezeController]属性完全替代了其他两个属性，并避免了一些其他问题。