uwp GridView Drop EventTriggerBehavior signature - xaml

Question

I'm working on a Drag and Drop Xaml Uwp application with multiple ComboBox and GridView. I experimented with it a bit in xaml code behind until I thought I knew where I was heading with the app. I then began moving my logic into a ViewModel, PlayPageViewModel, I'm using MvvM Light and Template 10. I have many events working using interactions. I've had the Drop working in codeBehind when I move it over to the view model I get Cannot find method named GvNewPlayList_OnDrop on object of type TheLolFx.UWP.T10.ViewModels.PlayPageViewModel that matches the expected signature.
Exception
Exception {System.ArgumentException: Cannot find method named GvNewPlayList_OnDrop on object of type TheLolFx.UWP.T10.ViewModels.PlayPageViewModel that matches the expected signature.
at Microsoft.Xaml.Interactions.Core.CallMethodAction.Execute(Object sender, Object parameter)
at Microsoft.Xaml.Interactivity.Interaction.ExecuteActions(Object sender, ActionCollection actions, Object parameter)
at Microsoft.Xaml.Interactions.Core.EventTriggerBehavior.OnEvent(Object sender, Object eventArgs)} System.Exception {System.ArgumentException}
Message
Message "System.ArgumentException: Cannot find method named GvNewPlayList_OnDrop on object of type TheLolFx.UWP.T10.ViewModels.PlayPageViewModel that matches the expected signature.\r\n at Microsoft.Xaml.Interactions.Core.CallMethodAction.Execute(Object sender, Object parameter)\r\n at Microsoft.Xaml.Interactivity.Interaction.ExecuteActions(Object sender, ActionCollection actions, Object parameter)\r\n at Microsoft.Xaml.Interactions.Core.EventTriggerBehavior.OnEvent(Object sender, Object eventArgs)" string
I used the signature that was generated in the code behind. The ContainerContentChangingis fired in the ViewModel As you can see commented out I tried with just object too.
What is the correct signature?
XAML
<GridView x:Name="GvNewPlayList"
RelativePanel.Below="CbPlayListEditor"
Visibility="{Binding LbNewPlayListVisibility}"
Background="BurlyWood"
Padding="5"
Header="New Play List"
ItemsSource="{Binding NewLocalSoundsPlayListsSelectedItem.LocalSfxV2s}"
CanDragItems="True"
AllowDrop="True"
CanReorderItems="True"
IsItemClickEnabled="True"
DragItemsStarting="LbNewPlayList_OnDragItemsStarting"
DragOver="LbNewPlayList_OnDragOver">
<interactivity:Interaction.Behaviors>
<core:EventTriggerBehavior EventName="Drop">
<core:CallMethodAction MethodName="GvNewPlayList_OnDrop"
TargetObject="{Binding Mode=OneWay}" />
</core:EventTriggerBehavior>
<core:EventTriggerBehavior EventName="ContainerContentChanging">
<core:CallMethodAction MethodName="GvLocalSoundsPlayListEditorContainerContentChangingAsync"
TargetObject="{Binding Mode=OneWay}" />
</core:EventTriggerBehavior>
</interactivity:Interaction.Behaviors>
<GridView.ItemTemplate>
<DataTemplate>
[...]
PlayPageViewModel
Exception fired on XAML attempting to target this method in the vm.
// private async void GvNewPlayList_OnDrop(object sender, object e)
// private async void GvNewPlayList_OnDrop()
private async void GvNewPlayList_OnDrop(object sender, DragEventArgs e)
{
e.AcceptedOperation = DataPackageOperation.Copy;
Logger.Log(this, "yup");
[...]
}
This one fires from the ContainerContentChanging event.
public async void GvLocalSoundsPlayListEditorContainerContentChangingAsync()
{
Logger.Log(this, $"GvLocalSoundsPlayListEditorContainerContentChangingAsync: {SelectedPlayList?.PlayListName}");
//_settings.CurrentPlayList = SelectedPlayList;
//LocalSounds = await _theLolFxV2DataServices.GetPlayListAsync(SelectedPlayList);
//NewLocalSoundsPlayListItems = await _theLolFxV2DataServices.GetPlayListAsync(CbPlayListEditorSelectedItem);
}

Answer 1

When using a CallMethodAction for invoking a method, the signature of the method should be like this: public void DoSomthing(). The reasons for the exception are:
GvNewPlayList_OnDrop is marked as private, it need mark as public;
It cannot contain any parameters.
So just modify its signature like that of the second method: public async void GvLocalSoundsPlayListEditorContainerContentChangingAsync()