Question

我正在为ObservableCollection开发一个Refresh（）扩展方法，它根据匹配的键添加，删除或替换项目（这意味着当绑定到DataGrid时，网格不会重新滚动，项目不会更改他们的位置，除非他们被删除）。

问题是当我替换ObservableCollection中的项目时，最后一个项目抛出ArgumentOutOfRangeException，我在这里缺少什么？

public static void Refresh<TItem, TKey>(this ObservableCollection<TItem> target, IEnumerable<TItem> source, Func<TItem, TKey> keySelector)
{
    var sourceDictionary = source.ToDictionary(keySelector);
    var targetDictionary = target.ToDictionary(keySelector);

    var newItems = sourceDictionary.Keys.Except(targetDictionary.Keys).Select(k => sourceDictionary[k]).ToList();
    var removedItems = targetDictionary.Keys.Except(sourceDictionary.Keys).Select(k => targetDictionary[k]).ToList();
    var updatedItems = (from eachKey in targetDictionary.Keys.Intersect(sourceDictionary.Keys)
                        select new
                        {
                            Old = targetDictionary[eachKey],
                            New = sourceDictionary[eachKey]
                        }).ToList();

    foreach (var updatedItem in updatedItems)
    {
        int index = target.IndexOf(updatedItem.Old);
        target[index] = updatedItem.New; // ArgumentOutOfRangeException is thrown here
    }

    foreach (var removedItem in removedItems)
    {
        target.Remove(removedItem);
    }

    foreach (var newItem in newItems)
    {
        target.Add(newItem);
    }
}

Answer 1

你有旧的和新的错误的方式。这样：

var updatedItems = (from eachKey in targetDictionary.Keys
                                              .Intersect(sourceDictionary.Keys)
                    select new
                    {
                        Old = targetDictionary[eachKey],
                        New = sourceDictionary[eachKey]
                    }).ToList();

应该是这样的：

var updatedItems = (from eachKey in targetDictionary.Keys
                                              .Intersect(sourceDictionary.Keys)
                    select new
                    {
                        New = targetDictionary[eachKey],
                        Old = sourceDictionary[eachKey]
                    }).ToList();

目前您正在寻找 new 值的索引，该值为-1 ......

替换ObservableCollection <t>中的项目时的ArgumentOutOfRangeException </t>

1 个答案: