How to access the parent viewmodel from inside a ListView.ItemTemplate? - xaml

Question

I have this simple ListView filled from an ObservableCollection. Once the list is bound, I would like to access the parent vm view model from inside this ItemTemplate so that I can bind the command called cmd_delete_mesh. How is this done for a UWP Xaml app (not wpf)?
<ListView x:Name="mesh_list" SelectedItem="{x:Bind vm.selected_mesh, Mode=TwoWay}" ItemsSource="{x:Bind vm.meshes}">
<ListView.ItemTemplate>
<DataTemplate>
<ListViewItem>
<Button Command="{Binding cmd_delete_mesh}"/>

Answer 1

You can do like so:
<ListView x:Name="mesh_list" SelectedItem="{x:Bind vm.selected_mesh, Mode=TwoWay}" ItemsSource="{x:Bind vm.meshes}">
<ListView.ItemTemplate>
<DataTemplate>
<ListViewItem>
<Button Command="{Binding ElementName=mesh_list, Path=DataContext.vm.cmd_delete_mesh}"/>

Answer 2

I do this from code unfortunately... I’ll post an example of my code soon

Answer 3

You could define your command in your model and declare an event in it. In your ViewModel, when you initialize the 'meshes' collection, you could register this event for every item in this collection. Then, when the command is executed, you just need to raise the event and do some operations in its event handler.
I made a simple code sample for your reference:
<ListView x:Name="mesh_list" SelectedItem="{x:Bind ViewModel.selected_mesh, Mode=TwoWay}" ItemsSource="{x:Bind ViewModel.meshes,Mode=OneWay}">
<ListView.ItemTemplate>
<DataTemplate x:DataType="local:SubTest">
<ListViewItem>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{x:Bind Name }"></TextBlock>
<Button Command="{x:Bind cmd_delete_mesh}" Content="delete"/>
</StackPanel>
</ListViewItem>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
ViewModel = new Test("test data");
}
private Test ViewModel { get; set; }
}
public class Test : ViewModelBase
{
public string Name { get; set; }
private SubTest _selected_mesh;
public SubTest selected_mesh
{
get { return _selected_mesh; }
set
{
if (_selected_mesh != value)
{
_selected_mesh = value;
RaisePropertyChanged("selected_mesh");
}
}
}
public ObservableCollection<SubTest> meshes { get; set; } = new ObservableCollection<SubTest>();
public Test(string name)
{
this.Name = name;
for (int i = 0; i < 10; i++)
{
var sub = new SubTest() { Name = "String " + i };
sub.DeleteParentItem += Test_DeleteParentItem;
meshes.Add(sub);
}
}
private void Test_DeleteParentItem()
{
if (selected_mesh != null)
{
DeleteItem(selected_mesh);
}
}
private void DeleteItem(SubTest subTest)
{
//TODO...
}
}
public class SubTest
{
public RelayCommand cmd_delete_mesh { get; set; }
public string Name { get; set; }
public event Action DeleteParentItem;
public SubTest()
{
cmd_delete_mesh = new RelayCommand(DeleteItem);
}
private void DeleteItem()
{
if (DeleteParentItem != null)
{
DeleteParentItem.Invoke();
}
}
}
Please note that the ViewModelBase and RelayCommand are from mvvmlight.
using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;