Question

我有一个带有网格控件DataGridViewDataGridView的WinForms应用。它与BindingSource绑定如下：

    interface IObj
    {
        int Code { get; set; }
    }

    ... 

    BindingList<IObj> list = <I am given this list from another module>;
    BindingSource bs = new BindingSource(list, "Code");
    myGrid.DataSource = bs;

现在我被要求改进这个旧的应用程序 - 让myGrid中的列可以排序。它应该不是由“int Code”排序，而是按字符串值排序（在运行时使用“int Code”计算）。

我无法扩展IObj接口为其添加新的属性进行排序。

是的 - 我知道有DataGridViewColumnSortMode.Programmatic;我可以为网格列处理ColumnHeaderMouseClick并在那里实现排序。如果我可以使用新属性扩展IObj - 这就足够了。 DataGridView有属性Sort我可以指定新IObj成员的名称，但不幸的是我无法触及IObj。

这个问题能以某种方式解决吗？

Answer 1

尝试使用。 Sortable Binding list

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();
    }
}

WinForms DataGridView：我自己的排序逻辑？

1 个答案: