【转】将Datagrid的SelectedItems输出到ViewModel的友好MVVM方式
An interesting question from one of the MVVM Light users today:
Is there an MVVM-friendly way to get a DataGrid’s SelectedItems into the ViewModel?
The issue there is as old as the DataGrid (that’s not very old but still): SelectedItem (singular) is a DependencyProperty and can be databound to a property in the ViewModel. SelectedItems (plural) is not a DependencyProperty.
Thankfully the answer is very simple: Use EventToCommand to call a Command in the ViewModel, and pass the SelectedItems collection as parameter. For example, if the command in the ViewModel is declared as follows:
public RelayCommand<IList> SelectionChangedCommand { get; private set; }
and (in the MainViewModel constructor):
1 SelectionChangedCommand = new RelayCommand<IList>( 2 items => 3 { 4 if (items == null) 5 { 6 NumberOfItemsSelected = 0; 7 return; 8 } 9 10 NumberOfItemsSelected = items.Count; 11 });
Then the XAML markup becomes:
<sdk:DataGrid x:Name="MyDataGrid" ItemsSource="{Binding Items}"> <i:Interaction.Triggers> <i:EventTrigger EventName="SelectionChanged"> <cmd:EventToCommand Command="{Binding SelectionChangedCommand}" CommandParameter="{Binding SelectedItems, ElementName=MyDataGrid}" /> </i:EventTrigger> </i:Interaction.Triggers> </sdk:DataGrid>
I slapped a quick sample and published it here (VS2010, SL4 but the concept works in SL3 and WPF too).
