Subsonic 3.0 and linq

Question

I play with Subsonic 3.0 SimpleRepository and try to get menus and menu items with a single linq request, but menu items are always zero

Menu

public class Menu
{
    public Menu()
    {
        MenuId = 0;
        MenuName = "";
        MenuItems = null;
    }
    public int MenuId { get; set; }
    public string MenuName { get; set; }
    public MenuItem MenuItems { get; set; }
}

MENUITEM

public class MenuItem
{
    public MenuItem()
    {
        MenuItemId = 0;
        MenuId = 0;
        MenuItemName = "";
    }
    public int MenuItemId { get; set; }
    public int MenuId { get; set; }
    public string MenuItemName { get; set; }
}

Linq request

var menus =  from m in _repo.All<Menu>()
             from mi in _repo.All<MenuItem>()
             where m.MenuItems.MenuItemId == mi.MenuItemId
             select new Menu
             {
                 MenuId = m.MenuId,
                 MenuName = m.MenuName,
                 MenuItems = {
                             MenuItemId = mi.MenuItemId,
                             MenuItemName = mi.MenuItemName
                        }
             };

Can someone tell me what I'm doing wrong here?

Answer 1

I think I found the actual answer to this problem. I rummaged through the SubSonic source and found that there are two types of projections of objects that are used when mapping a data object to objects: one for anonymous types and groupings and one for everything else:

Here is a snippet: Line 269 - 298 SubSonic.Linq.Structure.DbQueryProvider

IEnumerable<T> result;
Type type = typeof (T);
//this is so hacky - the issue is that the Projector below uses Expression.Convert, which is a bottleneck
//it about 10x slower than our ToEnumerable. Our ToEnumerable, however, stumbles on Anon types and groupings
//since it doesn't know how to instantiate them (I tried - not smart enough). So we do some trickery here.
    if (type.Name.Contains("AnonymousType") || type.Name.StartsWith("Grouping`") || type.FullName.StartsWith("System.")) {
    var reader = _provider.ExecuteReader(cmd);
    result = Project(reader, query.Projector);
    } else
    {
        using (var reader = _provider.ExecuteReader(cmd))
        {
            //use our reader stuff
            //thanks to Pascal LaCroix for the help here...
            var resultType = typeof (T);
            if (resultType.IsValueType)
            {
                result = reader.ToEnumerableValueType<T>();
            }
            else
            {
                result = reader.ToEnumerable<T>();
            }
        }
    }
    return result;

, SubSonic ToEnumerable datareader , . SQL Query Linq :

SELECT [t0].[Id], [t0].[ProductId], [t0].[ReleaseDate], [t0].[ReleasedBy], [t0].[ReleaseNumber], [t0].[RevisionNumber], [t0].[c0]
FROM (
  SELECT [t1].[Id], [t1].[ProductId], [t1].[ReleaseDate], [t1].[ReleasedBy], [t1].[ReleaseNumber], [t1].[RevisionNumber], (
    SELECT COUNT(*)
    FROM [dbo].[Install] AS t2
    WHERE ([t2].[ReleaseId] = [t1].[Id])
    ) AS c0
  FROM [dbo].[Release] AS t1
  ) AS t0
WHERE ([t0].[ProductId] = 2)

[t0]. [c0] NumberOfInstalls. , c0 .

: if 10x , .

Answer 2

, - . Subsonic 3.0. , . - . .

var result = from r in Release.All()
             let i = Install.All().Count(x => x.ReleaseId == r.Id)
             where r.ProductId == productId
             select new ReleaseInfo
             {
                 NumberOfInstalls = i,
                 Id = r.Id,
                 ProductId = r.ProductId,
                 ReleaseNumber = r.ReleaseNumber,
                 RevisionNumber = r.RevisionNumber,
                 ReleaseDate = r.ReleaseDate,
                 ReleasedBy = r.ReleasedBy
             };

Installs , , :

var result = from r in Release.All()
             let i = Install.All().Count(x => x.ReleaseId == r.Id)
             where r.ProductId == productId
             select new 
             {
                 NumberOfInstalls = i,
                 Id = r.Id,
                 ProductId = r.ProductId,
                 ReleaseNumber = r.ReleaseNumber,
                 RevisionNumber = r.RevisionNumber,
                 ReleaseDate = r.ReleaseDate,
                 ReleasedBy = r.ReleasedBy
             };

, , , :

var menus =  from m in _repo.All<Menu>()
             from mi in _repo.All<MenuItem>()
             where m.MenuItems.MenuItemId == mi.MenuItemId
             select new 
             {
                 MenuId = m.MenuId,
                 MenuName = m.MenuName,
                 MenuItems = new {
                             MenuItemId = mi.MenuItemId,
                             MenuItemName = mi.MenuItemName
                        }
             };

, . , ?:)