Entity Framework in WinForms

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.Entity;
using System.Data.Entity.Core.Objects.DataClasses;
using System.Diagnostics;

namespace EFWinforms
{
    /// <summary>
    /// IBindingList with support for sorting.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class EntityBindingList<T> :
        BindingList<T>,
        ITypedList,
        IBindingListView,
        IEntityBindingList
        where T : class
    {
        //----------------------------------------------------------------------------
        #region ** fields

        EntityDataSource _ds;
        DbSet<T> _set;
        EntityCollection<T> _coll;
        IEnumerable _query;
        string _name;
        PropertyDescriptor _sortProp;
        ListSortDirection _sortDir;
        bool _deferNotifications;
        int _addingNew;

        #endregion

        //----------------------------------------------------------------------------
        #region ** ctor

        /// <summary>
        /// Initializes a new instance of a <see cref="EntityBindingList"/>.
        /// </summary>
        /// <param name="dataSource"><see cref="EntityDataSource"/> that owns the entities on this list.</param>
        /// <param name="query"><see cref="IEnumerable"/> that provides the entities for this list.</param>
        /// <param name="name">A name for identifying this list in its parent (for hierarchical binding).</param>
        public EntityBindingList(EntityDataSource dataSource, IEnumerable query, string name)
        {
            _ds = dataSource;
            _set = query as DbSet<T>;
            _coll = query as EntityCollection<T>;
            _query = query;
            _name = name;

            // populate list
            if (dataSource != null && !dataSource.DesignMode)
            {
                // at run time, get the data
                Refresh();
            }
            else
            {
                // at design time, add one element to help with binding
                try
                {
                    AddNew();
                }
                catch { }
            }
        }
        /// <summary>
        /// Initializes a new instance of a <see cref="EntityBindingList"/>.
        /// </summary>
        /// <param name="query"><see cref="IEnumerable"/> that provides the entities for this list.</param>
        public EntityBindingList(IEnumerable query)
            : this(null, query, string.Empty) {}

        #endregion

        //----------------------------------------------------------------------------
        #region ** object model

        /// <summary>
        /// Gets the <see cref="EntityDataSource"/> that owns the elements on this list.
        /// </summary>
        public EntityDataSource DataSource
        {
            get { return _ds; }
        }
        /// <summary>
        /// Gets the <see cref="Type"/> of elements on this list.
        /// </summary>
        public Type ElementType
        {
            get { return typeof(T); }
        }
        /// <summary>
        /// Refreshes the list by re-loading all items from the source query.
        /// </summary>
        public void Refresh()
        {
            try
            {
                // suspend notifications until done
                _deferNotifications = true;

                // clear current items
                Clear();

                // add items in the query
                foreach (T item in EntitySet.GetActiveEntities(_query))
                {
                    if (ApplyFilter(item))
                    {
                        this.Add(item);
                    }
                }
    
                // apply sort if any
                if (IsSortedCore)
                {
                    ApplySortCore(_sortProp, _sortDir);
                }
            }
            finally
            {
                // done
                _deferNotifications = false;
                OnListChanged(new ListChangedEventArgs(ListChangedType.Reset, -1));
            }
        }

        #endregion

        //----------------------------------------------------------------------------
        #region ** overrides

        /// <summary>
        /// Raises the <see cref="ListChanged"/> event.
        /// </summary>
        /// <param name="e"><see cref="ListChangedEventArgs"/> that contains the event data.</param>
        protected override void OnListChanged(ListChangedEventArgs e)
        {
            if (!_deferNotifications)
            {
                base.OnListChanged(e);

                // refresh iff we are not adding a new item
                if (_addingNew == 0)
                {
                    if (e.ListChangedType == ListChangedType.ItemChanged ||
                        e.ListChangedType == ListChangedType.ItemAdded)
                    {
                        // refresh list (to honor filters)
                        if (_set == null && _query != null)
                        {
                            Refresh();
                        }

                        // refresh sort
                        if (_sortProp != null && e.PropertyDescriptor == _sortProp)
                        {
                            ApplySortCore(_sortProp, _sortDir);
                        }
                    }
                }
            }
        }
        /// <summary>
        /// Adds a new item to the end of the collection.
        /// </summary>
        /// <returns>The item that was added to the collection.</returns>
        protected override object AddNewCore()
        {
            // create new object
            var newObject = base.AddNewCore() as T;

            // add to entity set
            if (_set != null)
            {
                _set.Add(newObject);
            }
            else if (_coll != null)
            {
                _coll.Add(newObject);
            }

            // and return the new object
            return newObject;
        }
        /// <summary>
        /// Removes the item at the specified index.
        /// </summary>
        /// <param name="index">Index of the item to remove.</param>
        protected override void RemoveItem(int index)
        {
            // remove from entity set
            if (index > -1)
            {
                T item = this[index] as T;

                if (_set != null)
                {
                    _set.Remove(item);

                    // check that the entity was deleted
                    var ent = item as EntityObject;
                    if (ent != null)
                    {
                        Debug.Assert(
                            ent.EntityState == EntityState.Deleted ||
                            ent.EntityState == EntityState.Detached
                            );
                    }
                }
                else if (_coll != null)
                {
                    _coll.Remove(item);
                }
            }

            // and remove from this list
            base.RemoveItem(index);
        }
        /// <summary>
        /// Allow adding new only if we have a set.
        /// </summary>
        bool IBindingList.AllowNew
        {
            get { return _set != null || _coll != null; }
        }
        /// <summary>
        /// Allow removing only if we have a set.
        /// </summary>
        bool IBindingList.AllowRemove
        {
            get { return _set != null || _coll != null; }
        }
        protected override void OnAddingNew(AddingNewEventArgs e)
        {
            // BindingList<T> weirdness: EndNew is called twice instead of once
            _addingNew = 2;
            base.OnAddingNew(e);
        }
        public override void CancelNew(int itemIndex)
        {
            base.CancelNew(itemIndex);
            if (itemIndex > -1)
            {
                _addingNew--;
            }
        }
        public override void EndNew(int itemIndex)
        {
            base.EndNew(itemIndex);
            if (itemIndex > -1)
            {
                _addingNew--;
                if (_addingNew == 0 && _sortProp != null)
                {
                    ApplySortCore(_sortProp, _sortDir);
                }
            }
        }

        #endregion

        //----------------------------------------------------------------------------
        #region ** sorting support

        /// <summary>
        /// Gets a value indicating whether this list supports sorting.
        /// </summary>
        protected override bool SupportsSortingCore
        {
            get { return true; }
        }
        /// <summary>
        /// Gets the <see cref="PropertyDescriptor"/> that is used for sorting the list.
        /// </summary>
        protected override PropertyDescriptor SortPropertyCore
        {
            get { return _sortProp; }
        }
        /// <summary>
        /// Gets the <see cref="ListSortDirection"/> that is used for sorting the list.
        /// </summary>
        protected override ListSortDirection SortDirectionCore
        {
            get { return _sortDir; }
        }
        /// <summary>
        /// Gets a value indicating whether the list is currently sorted.
        /// </summary>
        protected override bool IsSortedCore
        {
            get { return _sortProp != null; }
        }
        /// <summary>
        /// Removes any sorting currently applied to the list.
        /// </summary>
        protected override void RemoveSortCore()
        {
            _sortProp = null;
            Refresh();
        }
        /// <summary>
        /// Sorts the items on the list.
        /// </summary>
        /// <param name="prop"><see cref="PropertyDescriptor"/> that specifies the property to sort on.</param>
        /// <param name="direction"><see cref="ListSortDirection"/> that specifies whether to sort the list in ascending or descending order.</param>
        protected override void ApplySortCore(PropertyDescriptor prop, ListSortDirection direction)
        {
            // get list to sort
            var items = this.Items as List<T>;

            // apply the sort
            if (items != null && prop != null)
            {
                // if this property is an EntityObject, get map to sort by display value
                ListDictionary map = null;
                if (DataSource != null && !prop.PropertyType.IsPrimitive) //typeof(EntityObject).IsAssignableFrom(prop.PropertyType))
                {
                    map = DataSource.GetLookupDictionary(prop.PropertyType);
                }

                // go sort the list
                var pc = new PropertyComparer<T>(prop, direction, map);
                items.Sort(pc);
            }

            // save new settings and notify listeners
            _sortProp = prop;
            _sortDir = direction;
            this.OnListChanged(new ListChangedEventArgs(ListChangedType.Reset, -1));
        }

        // PropertyComparer (used to sort the list)
        class PropertyComparer<TC> : IComparer<TC>
        {
            PropertyDescriptor _pd;
            ListSortDirection _direction;
            ListDictionary _map;

            public PropertyComparer(PropertyDescriptor pd, ListSortDirection direction, ListDictionary map)
            {
                _pd = pd;
                _direction = direction;
                _map = map;
            }
            public int Compare(TC x, TC y)
            {
                try
                {
                    // get values to compare
                    object o1 = _pd.GetValue(x);
                    object o2 = _pd.GetValue(y);

                    // honor mapping (to sort mapped columns by display value)
                    if (_map != null)
                    {
                        // use mapped values
                        o1 = _map[o1.ToString()];
                        o2 = _map[o2.ToString()];
                    }

                    // make sure values are comparable
                    var v1 = o1 as IComparable;
                    var v2 = o2 as IComparable;

                    // make the comparison
                    int cmp =
                        v1 == null && v2 == null ? 0 :
                        v1 == null ? +1 :
                        v2 == null ? -1 :
                        v1.CompareTo(v2);

                    // and honor sort direction
                    return _direction == ListSortDirection.Ascending ? +cmp : -cmp;
                }
                catch
                {
                    Debug.Assert(false, "comparison failed?");
                    return 0; // comparison failed...
                }
            }
        }

        #endregion

        //----------------------------------------------------------------------------
        #region ** ITypedList

        PropertyDescriptorCollection ITypedList.GetItemProperties(PropertyDescriptor[] listAccessors)
        {
            var list = new List<PropertyDescriptor>();
            foreach (PropertyDescriptor pd in TypeDescriptor.GetProperties(typeof(T)))
            {
                // skip base class properties (EntityState and EntityKey)
                if (pd.ComponentType == typeof(EntityObject))
                {
                    continue;
                }

                // add collection properties
                var type = pd.PropertyType;
                if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(ICollection<>))
                //if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(EntityCollection<>))
                {
                    list.Add(new CollectionPropertyDescriptor(DataSource, pd));
                    continue;
                }

                // add regular properties
                list.Add(pd);
            }
            return new PropertyDescriptorCollection(list.ToArray());
        }

        string ITypedList.GetListName(PropertyDescriptor[] listAccessors)
        {
            return _name;
        }

        #endregion

        //----------------------------------------------------------------------------
        #region ** IBindingListView

        string _filter;
        DataTable _dtFilter;
        void IBindingListView.ApplySort(ListSortDescriptionCollection sorts)
        {
            throw new NotImplementedException();
        }
        string IBindingListView.Filter
        {
            get { return _filter; }
            set 
            {
                _filter = value;
                UpdateFilterTable();
                Refresh();
            }
        }
        void IBindingListView.RemoveFilter()
        {
            _filter = null;
            Refresh();
        }
        ListSortDescriptionCollection IBindingListView.SortDescriptions
        {
            get { return null; }
        }
        bool IBindingListView.SupportsAdvancedSorting
        {
            get { return false; }
        }
        bool IBindingListView.SupportsFiltering
        {
            get { return true; }
        }
        bool ApplyFilter(T item)
        {
            bool pass = true;
            if (_dtFilter != null)
            {
                try
                {
                    // populate the row
                    var row = _dtFilter.Rows[0];
                    foreach (var pi in typeof(T).GetProperties())
                    {
                        row[pi.Name] = pi.GetValue(item, null);
                    }

                    // compute the expression
                    pass = (bool)row["_filter"];
                }
                catch { }
            }
            return pass;
        }
        void UpdateFilterTable()
        {
            _dtFilter = null;
            if (!string.IsNullOrEmpty(_filter))
            {
                // build/rebuild data table
                var dt = new DataTable();
                foreach (var pi in typeof(T).GetProperties())
                {
                    var type = pi.PropertyType;
                    var nt = Nullable.GetUnderlyingType(type);
                    if (nt != null)
                    {
                        type = nt;
                    }
                    dt.Columns.Add(pi.Name, type);
                }

                // add calculated column that contains the filter
                dt.Columns.Add("_filter", typeof(bool), _filter);

                // create a single row for evaluating expressions
                if (dt.Rows.Count == 0)
                {
                    dt.Rows.Add(dt.NewRow());
                }

                // done, save table
                _dtFilter = dt;
            }
        }

        #endregion
    }

    // property descriptor that converts EntityCollection<T> properties into
    // EntityBindingList properties.
    class CollectionPropertyDescriptor : PropertyDescriptor
    {
        EntityDataSource _ds;
        PropertyDescriptor _pd;
        Type _listType;

        public CollectionPropertyDescriptor(EntityDataSource ds, PropertyDescriptor pd)
            : base(pd.Name, null)
        {
            _ds = ds;
            _pd = pd;
            var elementType = _pd.PropertyType.GetGenericArguments()[0];
            _listType = typeof(EntityBindingList<>);
            _listType = _listType.MakeGenericType(elementType);
        }
        public override string Name
        {
            get { return _pd.Name; }
        }
        public override bool IsReadOnly
        {
            get { return _pd.IsReadOnly; }
        }
        public override void ResetValue(object component)
        {
            _pd.ResetValue(component);
        }
        public override bool CanResetValue(object component)
        {
            return _pd.CanResetValue(component);
        }
        public override bool ShouldSerializeValue(object component)
        {
            return _pd.ShouldSerializeValue(component);
        }
        public override Type ComponentType
        {
            get { return _pd.ComponentType; }
        }
        public override Type PropertyType
        {
            get { return _listType; }
        }
        public override object GetValue(object component)
        {
            return Activator.CreateInstance(_listType, _ds, (IEnumerable)_pd.GetValue(component), Name);
        }
        public override void SetValue(object component, object value)
        {
            _pd.SetValue(component, value);
            OnValueChanged(component, EventArgs.Empty);
        }
    }

    /// <summary>
    /// Extends the IBindingListView with properties and methods relative to the entity set.
    /// </summary>
    public interface IEntityBindingList : IBindingListView
    {
        /// <summary>
        /// Gets the <see cref="EntityDataSource"/> that owns the elements on this list.
        /// </summary>
        EntityDataSource DataSource { get; }
        /// <summary>
        /// Gets the type of element on this list.
        /// </summary>
        Type ElementType { get; }
        /// <summary>
        /// Refresh the list by re-loading all items from the source query.
        /// </summary>
        void Refresh();
    }
}