Best approach for view model creation to handle single entity and list - return IQuerable

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Looking for input on the best approach/pattern to meet the following requirement for a view model class:

• Converts an IQueryable from a repository select to a IQueryable view model query <-- Works fine


• Converts a single instance of a db entity to a view model instance <-- is not working, returns NULL


• Both use a single method to map db entity to view model properties to avoid mapping replication

Example of what I am attempting, but it is not working...and seems maybe a bit of a hack:

public class WorkOrderDependencyViewModel : IEntity, IViewModel<WorkOrderDependency, WorkOrderDependencyViewModel>
{
    public int Id { get; set; } }
    public int WorkOrderHeaderId { get; set; }
    public int POHeaderId { get; set; }      
    public decimal RemainQty { get; set; }

    //Re-use this mapping logic for both converting a query and converting a single db entity instance. Used by Kendo Grids
    public IQueryable<WorkOrderDependencyViewModel> ConvertClassQueryToViewModelQuery(IQueryable<WorkOrderDependency> entityQuery)
    {
        var viewModelResultQuery = entityQuery
            .Select(x => new WorkOrderDependencyListViewModel()
            {
                Id = x.Id,
                WorkOrderHeaderId = x.WorkOrderHeaderId,
                POHeaderId = x.PODetail.POHeaderId,
                RemainQty = x.PODetail.QtyOrdered - x.PODetail.QtyReceived
            }
        );

        return viewModelResultQuery;
    }

    //convert single instance of db entity to view model, but use existing mapping logic from above method
    public WorkOrderDependencyViewModel ConvertClassToViewModel(WorkOrderDependency entity)
    {
        var entityList = new List<WorkOrderDependency>();
        entityList.Add(entity);
        var viewModel = ConvertClassQueryToViewModelQuery(entityList.AsQueryable()).FirstOrDefault() as WorkOrderDependencyViewModel;
        return viewModel; <------ viewModel is NULL
    }
}

Why is viewModel returning NULL?

asked 41 secs ago

Chad Richardson

1,119

Best approach for view model creation to handle single entity and list - return IQuerable