反向排序BindingList (Reverse sort a BindingList)

反向排序BindingList (Reverse sort a BindingList)

我有一个自定义类继承自BindingList（T） ，我绑定到一个DataGrid 。

但是， DataGrid正从上到下填充，我希望从下到上填充DataGrid 。 所以底部项目是索引0而不是顶部项目。

我如何更改我的BindingList（T）以便DataGrid反向读取它？

I have a custom class that inherits from BindingList(T) that I am binding to a DataGrid.

However, the DataGrid is being populated from the top down and I want it populated from the bottom up. So the bottom item is index 0 rather then the top item.

How can I change my BindingList(T) so that the DataGrid reads it in reverse?

最满意答案

这篇关于CodeProject.com的关于实现可排序的BindingList的文章可能会对你有所帮助。

它有一个很好的绑定列表的通用包装，使它可以排序：

public class MySortableBindingList<T> : BindingList<T> { // reference to the list provided at the time of instantiation List<T> originalList; ListSortDirection sortDirection; PropertyDescriptor sortProperty; // function that refereshes the contents // of the base classes collection of elements Action<MySortableBindingList<T>, List<T>> populateBaseList = (a, b) => a.ResetItems(b); // a cache of functions that perform the sorting // for a given type, property, and sort direction static Dictionary<string, Func<List<T>, IEnumerable<T>>> cachedOrderByExpressions = new Dictionary<string, Func<List<T>, IEnumerable<T>>>(); public MySortableBindingList() { originalList = new List<T>(); } public MySortableBindingList(IEnumerable<T> enumerable) { originalList = enumerable.ToList(); populateBaseList(this, originalList); } public MySortableBindingList(List<T> list) { originalList = list; populateBaseList(this, originalList); } protected override void ApplySortCore(PropertyDescriptor prop, ListSortDirection direction) { /* Look for an appropriate sort method in the cache if not found . Call CreateOrderByMethod to create one. Apply it to the original list. Notify any bound controls that the sort has been applied. */ sortProperty = prop; var orderByMethodName = sortDirection == ListSortDirection.Ascending ? "OrderBy" : "OrderByDescending"; var cacheKey = typeof(T).GUID + prop.Name + orderByMethodName; if (!cachedOrderByExpressions.ContainsKey(cacheKey)) { CreateOrderByMethod(prop, orderByMethodName, cacheKey); } ResetItems(cachedOrderByExpressions[cacheKey](originalList).ToList()); ResetBindings(); sortDirection = sortDirection == ListSortDirection.Ascending ? ListSortDirection.Descending : ListSortDirection.Ascending; } private void CreateOrderByMethod(PropertyDescriptor prop, string orderByMethodName, string cacheKey) { /* Create a generic method implementation for IEnumerable<T>. Cache it. */ var sourceParameter = Expression.Parameter(typeof(List<T>), "source"); var lambdaParameter = Expression.Parameter(typeof(T), "lambdaParameter"); var accesedMember = typeof(T).GetProperty(prop.Name); var propertySelectorLambda = Expression.Lambda(Expression.MakeMemberAccess(lambdaParameter, accesedMember), lambdaParameter); var orderByMethod = typeof(Enumerable).GetMethods() .Where(a => a.Name == orderByMethodName && a.GetParameters().Length == 2) .Single() .MakeGenericMethod(typeof(T), prop.PropertyType); var orderByExpression = Expression.Lambda<Func<List<T>, IEnumerable<T>>>( Expression.Call(orderByMethod, new Expression[] { sourceParameter, propertySelectorLambda }), sourceParameter); cachedOrderByExpressions.Add(cacheKey, orderByExpression.Compile()); } protected override void RemoveSortCore() { ResetItems(originalList); } private void ResetItems(List<T> items) { base.ClearItems(); for (int i = 0; i < items.Count; i++) { base.InsertItem(i, items[i]); } } protected override bool SupportsSortingCore { get { // indeed we do return true; } } protected override ListSortDirection SortDirectionCore { get { return sortDirection; } } protected override PropertyDescriptor SortPropertyCore { get { return sortProperty; } } protected override void OnListChanged(ListChangedEventArgs e) { originalList = base.Items.ToList(); } }

This article on CodeProject.com about implementing sortable BindingList might help you.

It has a nice generic wrapper for binding list that makes it sortable:

public class MySortableBindingList<T> : BindingList<T> { // reference to the list provided at the time of instantiation List<T> originalList; ListSortDirection sortDirection; PropertyDescriptor sortProperty; // function that refereshes the contents // of the base classes collection of elements Action<MySortableBindingList<T>, List<T>> populateBaseList = (a, b) => a.ResetItems(b); // a cache of functions that perform the sorting // for a given type, property, and sort direction static Dictionary<string, Func<List<T>, IEnumerable<T>>> cachedOrderByExpressions = new Dictionary<string, Func<List<T>, IEnumerable<T>>>(); public MySortableBindingList() { originalList = new List<T>(); } public MySortableBindingList(IEnumerable<T> enumerable) { originalList = enumerable.ToList(); populateBaseList(this, originalList); } public MySortableBindingList(List<T> list) { originalList = list; populateBaseList(this, originalList); } protected override void ApplySortCore(PropertyDescriptor prop, ListSortDirection direction) { /* Look for an appropriate sort method in the cache if not found . Call CreateOrderByMethod to create one. Apply it to the original list. Notify any bound controls that the sort has been applied. */ sortProperty = prop; var orderByMethodName = sortDirection == ListSortDirection.Ascending ? "OrderBy" : "OrderByDescending"; var cacheKey = typeof(T).GUID + prop.Name + orderByMethodName; if (!cachedOrderByExpressions.ContainsKey(cacheKey)) { CreateOrderByMethod(prop, orderByMethodName, cacheKey); } ResetItems(cachedOrderByExpressions[cacheKey](originalList).ToList()); ResetBindings(); sortDirection = sortDirection == ListSortDirection.Ascending ? ListSortDirection.Descending : ListSortDirection.Ascending; } private void CreateOrderByMethod(PropertyDescriptor prop, string orderByMethodName, string cacheKey) { /* Create a generic method implementation for IEnumerable<T>. Cache it. */ var sourceParameter = Expression.Parameter(typeof(List<T>), "source"); var lambdaParameter = Expression.Parameter(typeof(T), "lambdaParameter"); var accesedMember = typeof(T).GetProperty(prop.Name); var propertySelectorLambda = Expression.Lambda(Expression.MakeMemberAccess(lambdaParameter, accesedMember), lambdaParameter); var orderByMethod = typeof(Enumerable).GetMethods() .Where(a => a.Name == orderByMethodName && a.GetParameters().Length == 2) .Single() .MakeGenericMethod(typeof(T), prop.PropertyType); var orderByExpression = Expression.Lambda<Func<List<T>, IEnumerable<T>>>( Expression.Call(orderByMethod, new Expression[] { sourceParameter, propertySelectorLambda }), sourceParameter); cachedOrderByExpressions.Add(cacheKey, orderByExpression.Compile()); } protected override void RemoveSortCore() { ResetItems(originalList); } private void ResetItems(List<T> items) { base.ClearItems(); for (int i = 0; i < items.Count; i++) { base.InsertItem(i, items[i]); } } protected override bool SupportsSortingCore { get { // indeed we do return true; } } protected override ListSortDirection SortDirectionCore { get { return sortDirection; } } protected override PropertyDescriptor SortPropertyCore { get { return sortProperty; } } protected override void OnListChanged(ListChangedEventArgs e) { originalList = base.Items.ToList(); } }