Rock.Model.GroupService.GetAllDescendents C# (CSharp) Method

        public IEnumerable<Group> GetAllDescendents( int parentGroupId )
        {
            return this.ExecuteQuery(
                @"
                with CTE as (
                select * from [Group] where [ParentGroupId]={0}
                union all
                select [a].* from [Group] [a]
                inner join CTE pcte on pcte.Id = [a].[ParentGroupId]
                )
                select * from CTE
                ", parentGroupId );
        }

        /// <summary>
        /// Loads the groups.
        /// </summary>
        private void LoadDropDowns()
        {
            var groupEntityType = EntityTypeCache.Read( typeof( Group ) );
            var currentGroup = RockPage.GetCurrentContext( groupEntityType ) as Group;

            var groupIdString = Request.QueryString["groupId"];
            if ( groupIdString != null )
            {
                var groupId = groupIdString.AsInteger();

                if ( currentGroup == null || currentGroup.Id != groupId )
                {
                    currentGroup = SetGroupContext( groupId, false );
                }
            }

            var parts = ( GetAttributeValue( "GroupFilter" ) ?? string.Empty ).Split( '|' );
            Guid? groupTypeGuid = null;
            Guid? rootGroupGuid = null;

            if ( parts.Length >= 1 )
            {
                groupTypeGuid = parts[0].AsGuidOrNull();
                if ( parts.Length >= 2 )
                {
                    rootGroupGuid = parts[1].AsGuidOrNull();
                }
            }

            var rockContext = new RockContext();
            var groupService = new GroupService( rockContext );
            var groupTypeService = new GroupTypeService( rockContext );
            IQueryable<Group> qryGroups = null;

            // if rootGroup is set, use that as the filter.  Otherwise, use GroupType as the filter
            if ( rootGroupGuid.HasValue )
            {
                var rootGroup = groupService.Get( rootGroupGuid.Value );
                if ( rootGroup != null )
                {
                    qryGroups = groupService.GetAllDescendents( rootGroup.Id ).AsQueryable();
                }
            }
            else if ( groupTypeGuid.HasValue )
            {
                SetGroupTypeContext( groupTypeGuid );

                if ( GetAttributeValue( "IncludeGroupTypeChildren" ).AsBoolean() )
                {
                    var childGroupTypeGuids = groupTypeService.Queryable().Where( t => t.ParentGroupTypes.Select( p => p.Guid ).Contains( groupTypeGuid.Value ) )
                        .Select( t => t.Guid ).ToList();

                    qryGroups = groupService.Queryable().Where( a => childGroupTypeGuids.Contains( a.GroupType.Guid ) );
                }
                else
                {
                    qryGroups = groupService.Queryable().Where( a => a.GroupType.Guid == groupTypeGuid.Value );
                }
            }

            // no results
            if ( qryGroups == null )
            {
                nbSelectGroupTypeWarning.Visible = true;
                lCurrentSelection.Text = string.Empty;
                rptGroups.Visible = false;
            }
            else
            {
                nbSelectGroupTypeWarning.Visible = false;
                rptGroups.Visible = true;

                lCurrentSelection.Text = currentGroup != null ? currentGroup.ToString() : GetAttributeValue( "NoGroupText" );

                var groupList = qryGroups.OrderBy( a => a.Order )
                    .ThenBy( a => a.Name ).ToList()
                    .Select( a => new GroupItem() { Name = a.Name, Id = a.Id } )
                    .ToList();

                // check if the group can be unselected
                if ( !string.IsNullOrEmpty( GetAttributeValue( "ClearSelectionText" ) ) )
                {
                    var blankGroup = new GroupItem
                    {
                        Name = GetAttributeValue( "ClearSelectionText" ),
                        Id = Rock.Constants.All.Id
                    };

                    groupList.Insert( 0, blankGroup );
                }

                rptGroups.DataSource = groupList;
                rptGroups.DataBind();
            }
        }