It is not possible to implicitly convert the type 'System.Collections.Generic.List <T>' to 'System.Linq.IQueryable <T>'

Question

I am trying to create a query in my domain service (VS 2010 Silverlight Business Application) that returns validation results that return as a specific value, my database is configured as:

Locations a) Inspections b) InspectionItems c) InspectionReadings a) Areas b) Inspections c) InspectionItems d) InspectionReadings 

So, as you can see, there are inspection indications for places in places and places. I have a POCO named StatusList:

  public class StatusList { [Key] [Editable(false)] public Guid ID { get; set; } public string LocationName { get; set; } public DateTime LastInspectionDate { get; set; } public string Status { get; set; } } 

which I use to return the query results:

  public IQueryable<StatusList> GetLocationStatus() { var status = (from location in this.ObjectContext.Locations where location.InspectionReadings.Status == value orderby a.DateTaken select new LocationStatusList() { ID = a.ID, LocationName = d.Name, }).ToList<StatusList>(); return status; } 

unfortunately, it returns an error in the title, and I have no idea why, since the list is clearly an element of the list, and I converted the results

 .ToList<LocationStatusList> 

Answer 1

The problem is that you called ToList() . You announced that you are returning an IQueryable<LocationStatusList> , and List<T> does not implement IQueryable<T> .

Options (select one):

• Delete the ToList call
• Change the return type to IEnumerable<LocationStatusList> , IList<LocationStatusList> or possibly List<LocationStatusList>

• Call AsQueryable() after ToList() :

   ... as before ... .ToList().AsQueryable(); 

Note that you do not need a type argument in the ToList call - it is the same as the compiler anyway.