1.一种源绑定方式：
您必须使用SelectionChanged 事件。最简单的方法是在代码隐藏中编写事件处理程序以将选定项“绑定”到视图模型。
//ViewModel
public ICollectionView BusinessCollection {get; set;}
public List<YourBusinessItem> SelectedObject {get; set;}
//Codebehind
private void ListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
var viewmodel = (ViewModel) DataContext;
viewmodel.SelectedItems = listview.SelectedItems
.Cast<YourBusinessItem>()
.ToList();
}
这仍然符合 MVVM 设计，因为视图和视图模型的职责是分开的。您在代码隐藏中没有任何逻辑，并且视图模型是干净且可测试的。
2。两种方式绑定：
如果您还需要更新视图，当视图模型更改时，您必须附加到 ViewModel 的 PropertyChanged 事件和选定项的 CollectionChanged 事件。当然你可以在代码隐藏中做到这一点，但在这种情况下，我会创建一些更可重用的东西：
//ViewModel
public ObservableCollection<YourBusinessItem> SelectedObject {get; set;}
//in codebehind:
var binder = new SelectedItemsBinder(listview, viewmodel.SelectedItems);
binder.Bind();
或者可以创建自定义附加属性，因此您可以在 xaml 中使用绑定语法：
<ListView local:ListViewExtensions.SelectedValues="{Binding SelectedItem}" .../>
public class SelectedItemsBinder
{
private ListView _listView;
private IList _collection;
public SelectedItemsBinder(ListView listView, IList collection)
{
_listView = listView;
_collection = collection;
_listView.SelectedItems.Clear();
foreach (var item in _collection)
{
_listView.SelectedItems.Add(item);
}
}
public void Bind()
{
_listView.SelectionChanged += ListView_SelectionChanged;
if (_collection is INotifyCollectionChanged)
{
var observable = (INotifyCollectionChanged) _collection;
observable.CollectionChanged += Collection_CollectionChanged;
}
}
public void UnBind()
{
if (_listView != null)
_listView.SelectionChanged -= ListView_SelectionChanged;
if (_collection != null && _collection is INotifyCollectionChanged)
{
var observable = (INotifyCollectionChanged) _collection;
observable.CollectionChanged -= Collection_CollectionChanged;
}
}
private void Collection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
foreach (var item in e.NewItems ?? new object[0])
{
if (!_listView.SelectedItems.Contains(item))
_listView.SelectedItems.Add(item);
}
foreach (var item in e.OldItems ?? new object[0])
{
_listView.SelectedItems.Remove(item);
}
}
private void ListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
foreach (var item in e.AddedItems ?? new object[0])
{
if (!_collection.Contains(item))
_collection.Add(item);
}
foreach (var item in e.RemovedItems ?? new object[0])
{
_collection.Remove(item);
}
}
}
附加属性实现
public class ListViewExtensions
{
private static SelectedItemsBinder GetSelectedValueBinder(DependencyObject obj)
{
return (SelectedItemsBinder)obj.GetValue(SelectedValueBinderProperty);
}
private static void SetSelectedValueBinder(DependencyObject obj, SelectedItemsBinder items)
{
obj.SetValue(SelectedValueBinderProperty, items);
}
private static readonly DependencyProperty SelectedValueBinderProperty = DependencyProperty.RegisterAttached("SelectedValueBinder", typeof(SelectedItemsBinder), typeof(ListViewExtensions));
public static readonly DependencyProperty SelectedValuesProperty = DependencyProperty.RegisterAttached("SelectedValues", typeof(IList), typeof(ListViewExtensions),
new FrameworkPropertyMetadata(null, OnSelectedValuesChanged));
private static void OnSelectedValuesChanged(DependencyObject o, DependencyPropertyChangedEventArgs value)
{
var oldBinder = GetSelectedValueBinder(o);
if (oldBinder != null)
oldBinder.UnBind();
SetSelectedValueBinder(o, new SelectedItemsBinder((ListView)o, (IList)value.NewValue));
GetSelectedValueBinder(o).Bind();
}
public static void SetSelectedValues(Selector elementName, IEnumerable value)
{
elementName.SetValue(SelectedValuesProperty, value);
}
public static IEnumerable GetSelectedValues(Selector elementName)
{
return (IEnumerable)elementName.GetValue(SelectedValuesProperty);
}
}