[C#] 實現 DataGridView 標頭自動排序

1.建立SortableBindingList類別，繼承BindingList，實作排序功能。

    public class SortableBindingList<T> : BindingList<T>
    {
        private readonly Dictionary<Type, PropertyComparer<T>> comparers;
        private bool isSorted;
        private ListSortDirection listSortDirection;
        private PropertyDescriptor propertyDescriptor;

        public SortableBindingList()
            : base(new List<T>())
        {
            this.comparers = new Dictionary<Type, PropertyComparer<T>>();
        }

        public SortableBindingList(IEnumerable<T> enumeration)
            : base(new List<T>(enumeration))
        {
            this.comparers = new Dictionary<Type, PropertyComparer<T>>();
        }

        protected override bool SupportsSortingCore
        {
            get { return true; }
        }

        protected override bool IsSortedCore
        {
            get { return this.isSorted; }
        }

        protected override PropertyDescriptor SortPropertyCore
        {
            get { return this.propertyDescriptor; }
        }

        protected override ListSortDirection SortDirectionCore
        {
            get { return this.listSortDirection; }
        }

        protected override bool SupportsSearchingCore
        {
            get { return true; }
        }

        protected override void ApplySortCore(PropertyDescriptor property, ListSortDirection direction)
        {
            List<T> itemsList = (List<T>)this.Items;

            Type propertyType = property.PropertyType;
            PropertyComparer<T> comparer;
            if (!this.comparers.TryGetValue(propertyType, out comparer))
            {
                comparer = new PropertyComparer<T>(property, direction);
                this.comparers.Add(propertyType, comparer);
            }

            comparer.SetPropertyAndDirection(property, direction);
            itemsList.Sort(comparer);

            this.propertyDescriptor = property;
            this.listSortDirection = direction;
            this.isSorted = true;

            this.OnListChanged(new ListChangedEventArgs(ListChangedType.Reset, -1));
        }

        protected override void RemoveSortCore()
        {
            this.isSorted = false;
            this.propertyDescriptor = base.SortPropertyCore;
            this.listSortDirection = base.SortDirectionCore;

            this.OnListChanged(new ListChangedEventArgs(ListChangedType.Reset, -1));
        }

        protected override int FindCore(PropertyDescriptor property, object key)
        {
            int count = this.Count;
            for (int i = 0; i < count; ++i)
            {
                T element = this[i];
                if (property.GetValue(element).Equals(key))
                {
                    return i;
                }
            }

            return -1;
        }
    }

    public class PropertyComparer<T> : IComparer<T>
    {
        private readonly IComparer comparer;
        private PropertyDescriptor propertyDescriptor;
        private int reverse;

        public PropertyComparer(PropertyDescriptor property, ListSortDirection direction)
        {
            this.propertyDescriptor = property;
            Type comparerForPropertyType = typeof(Comparer<>).MakeGenericType(property.PropertyType);
            this.comparer = (IComparer)comparerForPropertyType.InvokeMember("Default", BindingFlags.Static | BindingFlags.GetProperty | BindingFlags.Public, null, null, null);
            this.SetListSortDirection(direction);
        }

        #region IComparer<T> Members

        public int Compare(T x, T y)
        {
            return this.reverse * this.comparer.Compare(this.propertyDescriptor.GetValue(x), this.propertyDescriptor.GetValue(y));
        }

        #endregion

        private void SetPropertyDescriptor(PropertyDescriptor descriptor)
        {
            this.propertyDescriptor = descriptor;
        }

        private void SetListSortDirection(ListSortDirection direction)
        {
            this.reverse = direction == ListSortDirection.Ascending ? 1 : -1;
        }

        public void SetPropertyAndDirection(PropertyDescriptor descriptor, ListSortDirection direction)
        {
            this.SetPropertyDescriptor(descriptor);
            this.SetListSortDirection(direction);
        }
    }

2.將SortableBindingList物件繫結至DataGridView。

dataGridView.DataSource = new SortableBindingList<T>(List<T>之資料);