Question

I get this error in LINQ to Entities: LINQ to Entities does not recognize the method ‘System.String ToString()’ method.
How should I solve this common problem?

Note that FleetViewModel.DWTStart is a string and fleet.DWTStart is a nullable decimal.

            var qry = from fleet in _entitiesContext.Fleets
                  select new FleetViewModel
                  {
                      FleetID = fleet.FleetID,
                      FleetName = fleet.FleetName,
                      DWTStart = fleet.DWTStart.HasValue?fleet.DWTStart.Value.ToString():"",
                      DWTEnd = fleet.DWTEnd.HasValue ? fleet.DWTEnd.Value.ToString() : ""
                  };

Thanks.

Answer 1

Basically you need to do the final part in-process, which you can force with AsEnumerable:

var qry = _entitiesContext.Fleets
    .Select(fleet => new { fleet.FleetID,
                           fleet.FleetName,
                           fleet.DWTStart,
                           fleet.DWTEnd })
    .AsEnumerable() // Do the rest in-process
    .Select(fleet => new FleetViewModel {
        FleetID = fleet.FleetID,
        FleetName = fleet.FleetName,
        DWTStart = fleet.DWTStart.HasValue?fleet.DWTStart.Value.ToString():"",
        DWTEnd = fleet.DWTEnd.HasValue ? fleet.DWTEnd.Value.ToString() : ""
     });

If there’s nothing else in the entity apart from these four properties, you can skip the anonymous type to start with – it’s really only there to avoid fetching data you don’t need:

var qry = _entitiesContext.Fleets
    .AsEnumerable() // Do the rest in-process
    .Select(fleet => new FleetViewModel {
        FleetID = fleet.FleetID,
        FleetName = fleet.FleetName,
        DWTStart = fleet.DWTStart.HasValue?fleet.DWTStart.Value.ToString():"",
        DWTEnd = fleet.DWTEnd.HasValue ? fleet.DWTEnd.Value.ToString() : ""
     });