[DllImport("user32.dll", CharSet = CharSet.Auto)]
static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);

var items = from g in db.forum_SectionGroups
                        let allowedSections = g.Sections.Where(s => s.Permissions.Any(p => p.PermissionSetKey == "thread.view" && groupKeys.Contains(p.GroupKey) && p.Allow))
                        where allowedSections.Count() > 0
                        orderby g.Sequence ascending
                        select new {
                            Group = g,
                            AllowedSections = allowedSections
                        };

SELECT 
[Project6].[Sequence] AS [Sequence], 
[Project6].[Id] AS [Id], 
[Project6].[Title] AS [Title], 
[Project6].[Summary] AS [Summary], 
[Project6].[IsActive] AS [IsActive], 
[Project6].[C1] AS [C1], 
[Project6].[Id1] AS [Id1], 
[Project6].[Title1] AS [Title1], 
[Project6].[Summary1] AS [Summary1], 
[Project6].[SectionGroupId] AS [SectionGroupId], 
[Project6].[Sequence1] AS [Sequence1]
FROM ( SELECT 
	[Filter4].[Id] AS [Id], 
	[Filter4].[Title] AS [Title], 
	[Filter4].[Summary] AS [Summary], 
	[Filter4].[Sequence] AS [Sequence], 
	[Filter4].[IsActive] AS [IsActive], 
	[Filter7].[Id] AS [Id1], 
	[Filter7].[Title] AS [Title1], 
	[Filter7].[Summary] AS [Summary1], 
	[Filter7].[SectionGroupId] AS [SectionGroupId], 
	[Filter7].[Sequence] AS [Sequence1], 
	CASE WHEN ([Filter7].[Id] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]
	FROM   (SELECT [Project3].[Id] AS [Id], [Project3].[Title] AS [Title], [Project3].[Summary] AS [Summary], [Project3].[Sequence] AS [Sequence], [Project3].[IsActive] AS [IsActive]
		FROM ( SELECT 
			[Extent1].[Id] AS [Id], 
			[Extent1].[Title] AS [Title], 
			[Extent1].[Summary] AS [Summary], 
			[Extent1].[Sequence] AS [Sequence], 
			[Extent1].[IsActive] AS [IsActive], 
			(SELECT 
				COUNT(1) AS [A1]
				FROM ( SELECT 
					[Extent2].[Id] AS [Id]
					FROM [dbo].[forum_Section] AS [Extent2]
					WHERE [Extent1].[Id] = [Extent2].[SectionGroupId]
				)  AS [Project1]
				WHERE  EXISTS (SELECT 
					1 AS [C1]
					FROM [dbo].[forum_SectionPermission] AS [Extent3]
					WHERE ([Project1].[Id] = [Extent3].[SectionId]) AND (N'thread.view' = [Extent3].[PermissionSetKey]) AND (N'general' = [Extent3].[GroupKey]) AND ([Extent3].[Allow] = 1)
				)) AS [C1]
			FROM [dbo].[forum_SectionGroup] AS [Extent1]
		)  AS [Project3]
		WHERE [Project3].[C1] > 0 ) AS [Filter4]
	OUTER APPLY  (SELECT [Project4].[Id] AS [Id], [Project4].[Title] AS [Title], [Project4].[Summary] AS [Summary], [Project4].[SectionGroupId] AS [SectionGroupId], [Project4].[Sequence] AS [Sequence]
		FROM ( SELECT 
			[Extent4].[Id] AS [Id], 
			[Extent4].[Title] AS [Title], 
			[Extent4].[Summary] AS [Summary], 
			[Extent4].[SectionGroupId] AS [SectionGroupId], 
			[Extent4].[Sequence] AS [Sequence]
			FROM [dbo].[forum_Section] AS [Extent4]
			WHERE [Filter4].[Id] = [Extent4].[SectionGroupId]
		)  AS [Project4]
		WHERE  EXISTS (SELECT 
			1 AS [C1]
			FROM [dbo].[forum_SectionPermission] AS [Extent5]
			WHERE ([Project4].[Id] = [Extent5].[SectionId]) AND (N'thread.view' = [Extent5].[PermissionSetKey]) AND (N'general' = [Extent5].[GroupKey]) AND ([Extent5].[Allow] = 1)
		) ) AS [Filter7]
)  AS [Project6]
ORDER BY [Project6].[Sequence] ASC, [Project6].[Id] ASC, [Project6].[C1] ASC