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[英]WPF: Datagrid is updating header after adding or removing item at binding collection
[英]Optimize way of adding/removing/updating a new item in a collection
我想問一下我是否仍然可以優化代碼,因為目前,這就是我編寫代碼的方式。
這是通過使用MVVM,ObservableCollection和C#進行的
這是偽代碼
// ClientCollection is an ObservableCollection<T> object
// ClientLists is a List<T> object that came from the JSON data
//
// check our clients in ClientCollection
// if a client was removed in List<T>, then delete this client
// in our ClientCollection.
ToRemoveLists toremove;
{
for each Clients client in ClientCollection
var a = from b in ClientLists
where b.name == client.name
select b;
if a.count() == 0
toremove.Add a;
}
{ // remove client from ClientCollection
for each Clients client in toremove
ClientCollection.Remove client;
}
// now add new clients if there are any
// or update client info if this client exists
{
for each Clients client in ClientLists
var a = from b in ClientCollection
where b.name == client.name
select b;
if a.count() == 0
ClientCollection.Add clients
else
// update client info
// .
// .
// .
}
之所以這樣做,是因為使用.Clear()
似乎不是更新集合的好方法,首先它刷新整個列表,當您有成千上萬個項目時,它似乎在閃爍。.所以這就是我這樣做的原因。
表示一堆
有很多事情可以提高性能,但這是一個很好的起點,可以解決您的問題。 繼承自ObservableCollection並提供進行批量更改的方法,但僅引發單個事件,從而減少綁定更新:
public class BulkObservableCollection<T> : ObservableCollection<T>
{
public BulkObservableCollection()
{
}
public BulkObservableCollection(List<T> list) : base(list)
{
}
public BulkObservableCollection(IEnumerable<T> collection) : base(collection)
{
}
/// <summary>
/// Adds a range if items to the collection, causing a reset event to be fired.
/// </summary>
/// <param name="items"></param>
public void AddRange(IEnumerable<T> items)
{
if (items == null) throw new ArgumentNullException("items");
var intialCount = Items.Count;
Items.AddRange(items);
if (Items.Count != intialCount)
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
}
/// <summary>
/// Removes a range of items from the collection, causing a reset event to be fired.
/// </summary>
/// <param name="items"></param>
public void RemoveRange(IEnumerable<T> items)
{
if (items == null) throw new ArgumentNullException("items");
var intialCount = Items.Count;
foreach (var item in items)
Items.Remove(item);
if (Items.Count != intialCount)
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
}
public void Reset(IEnumerable<T> newItems)
{
if (newItems == null) throw new ArgumentNullException("newItems");
Items.Clear();
Items.AddRange(newItems);
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
}
}
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