I am using Exchange Web Services to try to get a list of all Outlook tasks which are not complete.

I have an instance of ExchangeService, and attempt to find all incomplete tasks like this:

```
SearchFilter searchFilter = new SearchFilter.IsNotEqualTo(TaskSchema.Status, TaskStatus.NotStarted);
FindItemsResults<Item> tasks = service.FindItems(WellKnownFolderName.Tasks, searchFilter, view);

```

However, on the last line, I get a "ServiceResponseException: The specified value is invalid for property." This seems weird to me because [the EWS documentation explicitly states](http://msdn.microsoft.com/en-us/library/microsoft.exchange.webservices.data.task.status%28v=exchg.80%29.aspx) that the Task.Status is supposed to be one of the TaskStatus enumeration values. Creating a SearchFilter which compares against a string value does not cause an exception, but I haven't tried any of the other enumeration options to see whether they give the same behavior.