WPF ObservableList調度程序線程

Question

我將一個項目從Windows窗體轉換爲WPF格式。目前，我已將所有數據綁定到元素。我現在在ObservableCollection提出一個問題，他說：

這種類型的CollectionView不會從調度線程不同的線程支持更改其 SourceCollection。

如何讓我的代碼線程安全？或者，如何將更改引導到Dispatcher線程？我已經看到了一些關於它的文章，但我很困惑如何將它應用到我自己的項目上。也許有人可以爲我闡明這一點？

這是我的ObservableList.cs代碼：

public class ObservableList<T> : ObservableCollection<T> 
{ 
    #region Private members 

    bool isInAddRange = false; 

    #endregion Private members 

    #region Public methods 

    /// <summary> 
    /// Creates a new empty ObservableList of the provided type. 
    /// </summary> 
    public ObservableList() 
    { 

    } 

    /// <summary> 
    /// Handles the event when a collection has changed. 
    /// </summary> 
    /// <param name="e"></param> 
    protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e) 
    { 
     // intercept this when it gets called inside the AddRange method. 
     if (!isInAddRange) 
      base.OnCollectionChanged(e); 
    } 

    /// <summary> 
    /// Adds a collection of items to the ObservableList. 
    /// </summary> 
    /// <param name="items"></param> 
    public void AddRange(IEnumerable<T> items) 
    { 
     isInAddRange = true; 
     foreach (T item in items) 
     { 
      Add(item); 
     } 

     isInAddRange = false; 

     var e = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add,items.ToList()); 
     base.OnCollectionChanged(e); 

    } 

    #endregion Public methods 
} 

}

編輯：答案通過YWM給出後，我改變了我的AddRange類：

public void AddRange(IEnumerable<T> items) 
{ 
    isInAddRange = true; 
    foreach (T item in items) 
    { 
     if (item != null) 
     { 
      Dispatcher.CurrentDispatcher.Invoke((Action)(() => 
       { 
        Add(item); 
       })); 
     } 
    } 

    isInAddRange = false; 

    var e = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add,items.ToList()); 
    base.OnCollectionChanged(e); 

} 

現在，我所有的ObservableList的是null。

Answer 1

我已經找到了一個乾淨的解決方案here。

這裏可能發生的問題不是應該在更改上調用UI線程，而是創建集合的線程！這並不一定是UI線程！

於是，我改變了我的代碼如下：

public class ObservableList<T> : ObservableCollection<T> 
{ 
    #region Private members 

    bool isInAddRange = false; 
    private readonly Dispatcher _currentDispatcher; 

    #endregion Private members 

    #region Public methods 

    /// <summary> 
    /// Creates a new empty ObservableList of the provided type. 
    /// </summary> 
    public ObservableList() 
    { 
     //Assign the current Dispatcher (owner of the collection) 
     _currentDispatcher = Dispatcher.CurrentDispatcher; 
    } 

    /// <summary> 
    /// Executes this action in the right thread 
    /// </summary> 
    ///<param name="action">The action which should be executed</param> 
    private void DoDispatchedAction(Action action) 
    { 
     if (_currentDispatcher.CheckAccess()) 
      action.Invoke(); 
     else 
      _currentDispatcher.Invoke(DispatcherPriority.DataBind, action); 
    } 

    /// <summary> 
    /// Handles the event when a collection has changed. 
    /// </summary> 
    /// <param name="e"></param> 
    protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e) 
    { 
     // intercept this when it gets called inside the AddRange method. 
     if (!isInAddRange) 
     { 
      DoDispatchedAction(() => base.OnCollectionChanged(e)); 
     } 
    } 

    /// <summary> 
    /// Adds a collection of items to the ObservableList. 
    /// </summary> 
    /// <param name="items"></param> 
    public void AddRange(IEnumerable<T> items) 
    { 
     isInAddRange = true; 
     foreach (T item in items) 
     { 
      if (item != null) 
       { 
        Add(item); 
      } 
     }  

     isInAddRange = false; 

     var e = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add,items.ToList()); 
     DoDispatchedAction(() => base.OnCollectionChanged(e)); 

    } 

    #endregion Public methods 
} 

我承認我還沒有測試AddRange()方法本身呢。鏈接的網站上給出的樣本是：

/// <summary> 
/// Inserts a item at the specified index 
/// </summary> 
///<param name="index">The index where the item should be inserted</param> 
///<param name="item">The item which should be inserted</param> 
protected override void InsertItem(int index, T item) 
{ 
    DoDispatchedAction(() => base.InsertItem(index, item)); 
} 

感謝大家的努力來幫助我！

Answer 2

當您將項目添加到ObservableCollection時，您需要調用UI調度程序線程來執行此操作。在課堂上使用它

Dispatcher.CurrentDispatcher.Invoke(() => 
    { 
     foreach (var myModel in itemsToAdd) 
     { 
        Images.Add(mymodel);     
     } 
    }); 

然後，

public ObservableList<String> Strings { get; set; } 

    public MyViewModel() 
    { 
     this.Strings = new ObservableList<string>(); 

     this.Strings.AddRange(new[] { "1", "2", "3", "4" }); 
    } 

Answer 3

雖然你現在呼籲在UI線程Add方法，你仍然引發事件：

這是像這樣做在調用線程的AddRange方法中。所以你最終會遇到同樣的問題，就像你做改變之前一樣。

試試這個：

public void AddRange(IEnumerable<T> items) 
{ 
    isInAddRange = true; 
    foreach (T item in items) 
    { 
     if (item != null) 
     { 
      Dispatcher.CurrentDispatcher.Invoke((Action)(() => 
       { 
        Add(item); 
       })); 
     } 
    } 

    isInAddRange = false; 

    var e = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add,items.ToList()); 
    Dispatcher.CurrentDispatcher.Invoke((Action)(() => 
    { 
     base.OnCollectionChanged(e); 
    }); 

}