Example refactoring large nested foreach loops with linq queries.

CheckinSchedule.cs

//
// THIS WORK IS LICENSED UNDER A CREATIVE COMMONS ATTRIBUTION-NONCOMMERCIAL-
// SHAREALIKE 3.0 UNPORTED LICENSE:
// http://creativecommons.org/licenses/by-nc-sa/3.0/
//
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.Composition;
using System.Linq;

using Rock.CheckIn;
using Rock.Model;

namespace Rock.Workflow.Action.CheckIn
{
    /// <summary>
    /// Loads the schedules available for each group
    /// </summary>
    [Description("Loads the schedules available for each group")]
    [Export(typeof(ActionComponent))]
    [ExportMetadata( "ComponentName", "Load Schedules" )]
    public class LoadSchedules : CheckInActionComponent
    {
        /// <summary>
        /// Executes the specified workflow.
        /// </summary>
        /// <param name="action">The workflow action.</param>
        /// <param name="entity">The entity.</param>
        /// <param name="errorMessages">The error messages.</param>
        /// <returns></returns>
        /// <exception cref="System.NotImplementedException"></exception>
        public override bool Execute( Model.WorkflowAction action, Data.IEntity entity, out List<string> errorMessages )
        {
             var checkInState = GetCheckInState( action, out errorMessages );
             if ( checkInState == null )
             {
                 return false;
             }

            var groupTypes = ( from f in checkInState.CheckIn.Families
                               where f.Selected
                                   from p in f.People
                                   where p.Selected
                                       from gt in p.GroupTypes
                                       where gt.Selected
                                       select gt ).ToList();

            var kioskGroupTypes = ( from kgt in checkInState.Kiosk.KioskGroupTypes
                                        from gt in groupTypes
                                        where gt.GroupType.Id == kgt.GroupType.Id
                                        select kgt ).ToList();

            // Find common groups for the selected location that match the kiosk's location
            var groups = ( from gt in groupTypes
                               from l in gt.Locations
                               where l.Selected
                                   from kgt in kioskGroupTypes
                                       from lkgt in kgt.KioskLocations
                                       where lkgt.Location.Id == l.Location.Id
                                           from g in l.Groups
                                           where g.Selected
                                           select g ).ToList();

            foreach (var group in groups)
            {
                var kioskGroup = kioskLocation.KioskGroups.FirstOrDefault( g => g.Group.Id == group.Group.Id );

                if ( kioskGroup == null )
                    continue;

                foreach ( var kioskSchedule in kioskGroup.KioskSchedules )
                {
                    if ( group.Schedules.Any( s => s.Schedule.Id != kioskSchedule.Schedule.Id ) )
                        continue;

                    var checkInSchedule = new CheckInSchedule
                        {
                            Schedule = kioskSchedule.Schedule.Clone( false )
                        };

                    group.Schedules.Add( checkInSchedule );
                }
            }

            SetCheckInState( action, checkInState );
            return true;
        }
    }
}