我有一个带有ItemsSource数据绑定的ComboBox。此ComboBox还侦听SelectionChanged事件。
但是,当ItemsSource更改时,将引发SelectionChanged事件。仅当ItemsSource是视图时才会发生这种情况。
有没有办法让SelectionChanged仅在用户执行时引发,而不是在ItemsSource属性发生更改时引发?
答案 0 :(得分:3)
如果您在代码中进行数据绑定,则可以在更改ItemsSource时取消订阅SelectionChanged。见下面的示例代码:
XAML:
<Window x:Class="WpfApplication1.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<StackPanel DataContextChanged="OnDataContextChanged">
<Button Content="Change items" Click="OnClick" />
<ComboBox Name="_cb" />
</StackPanel>
</Window>
代码背后:
public partial class Window1
{
public Window1()
{
InitializeComponent();
_cb.SelectionChanged += OnSelectionChanged;
DataContext = new VM();
}
private void OnClick(object sender, RoutedEventArgs e)
{
(DataContext as VM).UpdateItems();
}
private void OnSelectionChanged(object sender, SelectionChangedEventArgs e)
{
}
private void OnDataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
{
VM vm = DataContext as VM;
if (vm != null)
{
_cb.ItemsSource = vm.Items;
vm.PropertyChanged += OnVMPropertyChanged;
}
else
{
_cb.ItemsSource = null;
}
}
void OnVMPropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == "Items")
{
_cb.SelectionChanged -= OnSelectionChanged;
_cb.ItemsSource = (DataContext as VM).Items;
_cb.SelectionChanged += OnSelectionChanged;
}
}
}
public class VM : INotifyPropertyChanged
{
public VM()
{
UpdateItems();
}
public event PropertyChangedEventHandler PropertyChanged;
private List<string> _items = new List<string>();
public List<string> Items
{
get { return _items; }
set
{
_items = value;
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("Items"));
}
}
}
public void UpdateItems()
{
List<string> items = new List<string>();
for (int i = 0; i < 10; i++)
{
items.Add(_random.Next().ToString());
}
Items = items;
}
private static Random _random = new Random();
}
答案 1 :(得分:1)
我找到了方法:
private void comboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if(!ComboBox.IsDropDownOpen)
{
return;
}
///your code
}