Cannot implicitly convert type 'System.Linq.IQueryable<Project.Models.TaskTimeLine>' to 'Project.Models.TaskTimeLine'.

Question

I'm trying to pass a custom shaped class to a view, but I'm having a little trouble.

This is the error I'm getting.

Cannot implicitly convert type 'System.Linq.IQueryable' to 'Project.Models.TaskTimeLine'. An explicit conversion exists (are you missing a cast?)

This is the first time I've added a list to a class, and trying to pass one inside the other as it were.

Here is the class definition

  public class TaskTimeLine
  {
    public Task task { get; set; } // to hold a single object 
    public List<DateTime> scheduledDateTime { get; set; } // to hold a collection of    date times..

  }

The controller action is along the lines of this.

 [Authorize]
    public ActionResult Details2(int id)
    {
        TaskTimeLine task = new TaskTimeLine(); //create new instance of TaskTimeLine
        task = (IQueryable<TaskTimeLine>)taskRepository.GetTaskAndTimeLine(id);

        if (task == null)
            return View("NotFound");
        else
            return View("Details", task);
    }

All quite normal up until now, so I'm guessing maybe something is going wrong here.

  public IQueryable<TaskTimeLine> GetTaskAndTimeLine(int taskId)
    {
       TaskTimeLine taskTimeLine = new TaskTimeLine(); // create new main object
       taskTimeLine.scheduledDateTime = new List<DateTime>(); instanciate list object inside          
       taskTimeLine.task = db.Tasks.SingleOrDefault(d => d.id == taskId); read the record to fill the single task object


       /// Lots of logic is performed here to add loads of date records to the list object.

       /// If I add a break point and check the list I can see that all the date items have gone fine into the collection           


       return (IQueryable<TaskTimeLine>)taskTimeLine;
    }

The only reason I have so many odd casts in places is because it seemed that these helped the program compile. It currently doesn't compile, but I did get to, but when running the actual request it fails, with the same error message.

Can anyone help, also perhaps with add a more useful title for future people who are stuck with this kind of thing.

Answer 1

taskTimeLine is a TaskTimeLine; why would it also be an IQueryable<TaskTimeLine>?

  TaskTimeLine taskTimeLine = new TaskTimeLine(); // create new main object
  ....
  return (IQueryable<TaskTimeLine>)taskTimeLine;

IQueryable<T> relates to sources of data - not instances of the data itself (possible exception: Enumerable.AsQueryable()).

I suspect your method GetTaskAndTimeLine should simply return TaskTimeLine; and lose a lot of the casts...

public TaskTimeLine GetTaskAndTimeLine(int taskId)
{
   TaskTimeLine taskTimeLine = new TaskTimeLine(); // create new main object
   ...[snip]
   return taskTimeLine;
}
...
TaskTimeLine task = taskRepository.GetTaskAndTimeLine(id);

Answer 2

In the Details2 method:

TaskTimeLine task = new TaskTimeLine(); //create new instance of TaskTimeLine
task = (IQueryable<TaskTimeLine>)taskRepository.GetTaskAndTimeLine(id);

Here you are declaring task to be a TaskTimeLine, then trying to load an IQueryable<TaskTimeLine> into that variable. These types are not compatible.

Change your repository method to return a TaskTimeLine rather than an IQueryable (that will also get rid of the casting problem inside the GetTaskAndTimeLine method that Marc identifies), and remove the cast:

TaskTimeLine task = taskRepository.GetTaskAndTimeLine(id);