L2Q with Web API and EF: IQueryable interpreted as Dictionary

[manzanotti]

This is admittedly my first attempt to use L2Q, but I am getting an unfathomable error!

I am using Web Api (1.0) and Entity Framework (5.something).

I have a relatively simple object:

public class AgentTask
{
    public int Id { get; set; }
    public Guid AgentId { get; set; }
    public Guid PropertyId { get; set; }
    public TaskType Type { get; set; }
    public TaskStatus Status { get; set; }
    public Guid CreatedBy { get; set; }
    public DateTime CreatedDate { get; set; }
    public DateTime? SlaDeadline { get; set; }
    public DateTime? UpdatedDate { get; set; }
    public virtual Property Property { get; set; }
}

In my DbContext, I have a set of these:

public IDbSet<AgentTask> AgentTasks { get; set; }

I have a service layer that runs a simple query against this set:

public IQueryable<TaskViewModel> GetIncompleteTasks(Guid agentGuid)
{
    var tasks = _commonDatabaseContext.AgentTasks
        .Include(t => t.Property)
        .Where(
            t =>
                t.AgentId == agentGuid &&
                (!t.Property.IsRemoved.HasValue || (t.Property.IsRemoved.HasValue && !t.Property.IsRemoved.Value)) &&
                (t.Status != TaskStatus.Completed && t.Status != TaskStatus.Suspended && t.Status != TaskStatus.Deleted))
        .Select(a => new TaskViewModel()
        {
            Address = a.Property.Line1 + "," + a.Property.Line2,
            Description = a.Type,
            Id = a.Id,
            PropertyId = a.PropertyId,
            SlaDeadline = a.SlaDeadline,
            UpdatedDate = a.UpdatedDate
        });

    return tasks;
}

And this is called by my controller method:

[HttpGet]
[LinqToQueryable]
public IQueryable<TaskViewModel> GetIncompleteTasks()
{
    var loggedUser = _authenticator.GetUserId();

    if (loggedUser != null)
    {
        var result = _agentTaskListService.GetIncompleteTasks(loggedUser.Value);

        return result.AsQueryable();
    }

    throw new ArgumentException("Not Found");
}

I am calling my controller using a jQuery Ajax GET request. The url ends:

GetIncompleteTasks?$top=10&$skip=0&orderby=slaDeadline%20desc&$inlinecount=allpages

I get the following exception:

{
    "message": "An error has occurred.",
    "exceptionMessage": "The action 'GetIncompleteTasks' on controller 'AgentListing' with return type 'System.Collections.Generic.Dictionary`2[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.Object, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]' 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)\r\n   at System.Web.Http.QueryableAttribute.OnActionExecuted(HttpActionExecutedContext actionExecutedContext)\r\n   at System.Web.Http.Filters.ActionFilterAttribute.CallOnActionExecuted(HttpActionContext actionContext, HttpResponseMessage response, Exception exception)\r\n   at System.Web.Http.Filters.ActionFilterAttribute.<>c__DisplayClass2.<System.Web.Http.Filters.IActionFilter.ExecuteActionFilterAsync>b__0(HttpResponseMessage response)\r\n   at System.Threading.Tasks.TaskHelpersExtensions.<>c__DisplayClass41`2.<Then>b__40(Task`1 t)\r\n   at System.Threading.Tasks.TaskHelpersExtensions.ThenImpl[TTask,TOuterResult](TTask task, Func`2 continuation, CancellationToken cancellationToken, Boolean runSynchronously)"
}

I can put a breakpoint on the line return result.AsQueryable(); in the controller method, and it hits it fine.

Any suggestions as to what I've done wrong?

[beyond-code-github]

Hey thanks for the extra info. From the stack trace it looks like the Web API Queryable attribute/message handler is getting invoked somewhere along the line... is it possible that you've got this set up as a global filter in Webapiconfig.cs?

Basically this is the web api odata handler... so it's trying to process a response that has already been processed by linq to querystring and hence throwing an error.

Pete

[manzanotti]

Yep, that was the problem alright! Cheers for working that out. :)

[beyond-code-github]

No worries, enjoy Linq to Querystring!