在WPF/MVVM，如何實現以完美的方式

Question

在視圖，即XAML，我已在全選布爾值綁定到CheckBox控件

<CheckBox Grid.Row="5" Content="Select All" HorizontalAlignment="Left" Margin="0,5, 0, 0" IsChecked="{Binding Path=SelectAll, Mode=TwoWay}" Width="206"></CheckBox> 

「全選」功能和fullfill的全選作爲

public bool SelectAll 
    { 
     get { return this.Get<bool>("SelectAll"); } 
     set 
     { 
      this.Set<bool>("SelectAll", value); 
      if (this.SelectAllCommand.CanExecute(null)) 
       this.SelectAllCommand.Execute(value); 
     } 
    } 

是的，它看起來不錯，但我有一個問題...

當所有的複選框被手動選擇，在全選複選框應自動選擇......在那個時候，我們不不想要SelectAllCommand要執行的命令......

我該怎麼辦呢.....我知道也許這是一件容易的事，但如何完美地做到這一點....

謝謝你給我一些提前

Answer 1

建議嘗試

public bool? SelectedAll 
{ 
    get { return this.Get<bool?>("SelectedAll"); } 
    set 
    { 
     if(Equals(SelectedAll, value) == true) 
      return; 
     this.Set<bool?>("SelectedAll", value); 
     OnSelectedAllChanged(value); 
    } 
} 

private void SelectedAllChanged(bool? input) 
{ 
    //Stuff 
} 

Answer 2

你需要使用PropertyChanged事件項目的重新評估SelectAll值隨時選擇一個項目。

例如，

// Setup PropertyChange notification for each item in collection 
foreach(var item in MyCollection) 
{ 
    item.PropertyChanged += Item_PropertyChanged; 
} 

private bool _isSelectAllExecuting = false; 

// If the IsSelected property of an item changes, raise a property change 
// notification for SelectAll 
void Item_PropertyChanged(object sender, PropertyChangedEventArgs e) 
{ 
    if (!_isSelectAllExecuting && e.PropertyName == "IsSelected") 
     ReevaluateSelectAll(); 
} 

void ReevaluateSelectAll() 
{ 
    // Will evaluate true if no items are found that are not Selected 
    _selectAll = MyCollection.FirstOrDefault(p => !p.IsSelected) == null; 

    // Since we're setting private field instead of public one to avoid 
    // executing command in setter, we need to manually raise the 
    // PropertyChanged event to notify the UI it's been changed 
    RaisePropertyChanged("SelectAll"); 
} 

void SelectAll() 
{ 
    _isSelectAllExecuting = true; 

    foreach(var item in MyCollection) 
     item.IsSelected = true; 

    _isSelectAllExecuting = false; 
}