Dealing with Enums in Asp MVC Telerik Grid and Entity Framework - asp.net-mvc

Question

For web application in development(ASP.Net MVC), I'm using the telerik grid. The grid is bound to an IQueryable of my list, because it's a big table, and I want that telerik apply it's filter on the list, and then executes this result, not dowloading 10'000 rows(with the joined tables), and then with the filter, use only rows.
I'm using(and I really need it for this page, it's one of the key feature) the filter/order of the grid.
One of the main column(determining the kind of the data) is an enum.
The problem is that I get a "Specified type member is not supported in linq to entities" as soon as I'm trying to filter/sort it.
I've to bind it on the enum(and not the mapped int) because if I use the id, filters/order by will be on an int, and I can't expect that the user knows the id of the foreign table.
I just cannot implement myself again all grids parameter(located in url)(I assume, it's either I do everything, or nothing) and filter it correctly, order it correctly).
Do you have an idea of workaround?

Answer 1

I don't know how your Entity Model looks like but I'll suppose that you've something like this Model:
public partial class Project
{
public int Id { get; set; }
public string Name { get; set; }
public int Status { get; set; }
}
and the Status property represents your enum value then you've this enum:
public enum ProjectStatuses
{
Current = 1,
Started = 2,
Stopped = 3,
Finished = 4,
}
Then just create new ViewModel like this :
public class ProjectDetails
{
public int Id { get; set; }
public string Name { get; set; }
public int Status { get; set; }
public ProjectStatuses StatusValue { get { return (ProjectStatuses) Status; } }
// This property to display in telerik ClientTemplate
public string StatusName { get { return Enum.GetName(typeof (ProjectStatuses), Status ); } }
}
And because I love Extension Methods I'll add this one :
public static class ModelListExtensions
{
public static IQueryable<ProjectDetails> ToViewModelDetails(this IQueryable<Project> modelList)
{
return modelList.Select(m => new ProjectDetails
{
Id = m.Id,
Name = m.Name,
Status = m.Status,
};
}
}
Update :
Here is the Controller
public ActionResult Index()
{
int total;
var viewModel = getGridList(out total);
ViewBag.Total = total;
return View(viewModel);
}
//this Action to get ajax pages
[GridAction(EnableCustomBinding = true)]
public ActionResult ReGetIndex(GridCommand command, int roleId)
{
int total;
var list = getGridList(out total, roleId, command);
return View(new GridModel {Data = list, Total = total});
}
private IEnumerable<ProjectDetails> getGridList(out int total, GridCommand command = null)
{
command = command ?? new GridCommand {Page = 1};
foreach (var descriptor in command.SortDescriptors)
{
if (descriptor.Member == "StatusValue")
descriptor.Member = "Status";
}
foreach (FilterDescriptor descriptor in command.FilterDescriptors)
{
if (descriptor.Member == "StatusValue")
descriptor.Member = "Status";
}
var list = modelService.AllAsQuery()
.ToViewModelDetails() // To convert it to our ViewModel if we have one
.Where(command.FilterDescriptors);
total = list.Count();
return (IEnumerable<ProjectDetails>) list.Sort(command.SortDescriptors)
.Page(command.Page - 1, command.PageSize)
.GroupBy(command.GroupDescriptors).ToIList();
}
And this is the View
#model IEnumerable<ProjectDetails>
#{
Html.Telerik()
.Grid(Model)
.Name("ProjectsGrid")
.Sortable()
.Filterable()
.EnableCustomBinding(true)
.DataBinding(dataBinding => dataBinding
.Ajax()
.Select("ReGetIndex", "Projects"))
.Pageable(page => page.Style(GridPagerStyles.PageSizeDropDown | GridPagerStyles.NextPreviousAndNumeric).Total(ViewBag.Total))
.Columns(column =>
{
column.Bound(m => m.Id).Hidden(true);
column.Bound(m => m.Name);
column.Bound(m => m.StatusValue).ClientTemplate("<#= StatusName #>");
})
.Render();
}
Update :
If you want to enforce at least one sort order you could use something like this:
if (!command.SortDescriptors.Any())
{
command.SortDescriptors.Add(new SortDescriptor {Member = "YourDefaultProperty"});
}

Answer 2

You don't really have choice (or few annoying choices)
Wether you use a class instead of enum (but if you used an enum, that's because it was better).
Or you "pseudo-sort" your enum, and use the mapped int.
public enum TT
{
Brown = 0,
Green = 1
}
Of course, you'll have to check the actual datas (mapped int) in your DB and update them to conform to the new order (can't change enum order without impact). And you'll have to do that everytime you want to insert a value between existing enum values.
Or you wait for next EF / linq / c# version, which should have enum support in linq2entities