Question

So I am working on a windows phone app, and I am trying to move elements between two stackpanels (which are basically the two main screens of my app).

I have a pivot item which looks like this:

<controls:Pivot Title="MY APPLICATION">
<!--Pivot item one-->
    <controls:PivotItem Header="All Tokens">
        <ListBox x:Name="AllTokenListBox" Margin="0,0,0,0">
            <StackPanel x:Name="AllTokenStack"></StackPanel>
        </ListBox>
    </controls:PivotItem>
    <!--Pivot item two-->
    <controls:PivotItem Header="My Tokens">
        <ListBox x:Name="MyTokenListBox" Margin="0,0,0,0">
            <StackPanel x:Name="myTokenStack"></StackPanel>
        </ListBox>
    </controls:PivotItem>
</controls:Pivot>

When an item in the AllTokenStack is double tapped, I want to move it over to the myTokenStack. When I do that, the program crashes and says “The parameter is incorrect”.
It only does this if I am NOT in debugging mode (so if the phone is unplugged from the computer and I try to run the app). If it is in debugging mode, it works fine.

Here is the code I am using to transfer the object over:

private void container_Tap(object sender, GestureEventArgs e) {
    if (AllTokenContainer.Children.Contains(this)) {
       AllTokenContainer.Children.Remove(this);
       MyTokenContainer.Children.Add(this);      
    }
}

Does anyone know how to resolve this strange bug?

EDIT
Just to make it clear. The C# code is inside a class which I called Token. The Token class is a user control. It is that control which the user taps to trigger the event. Is this the wrong way to do it?

Stacktrace from the exception:

   at MS.Internal.XcpImports.CheckHResult(UInt32 hr)
   at MS.Internal.XcpImports.Collection_AddValue[T](PresentationFrameworkCollection`1 collection, CValue value)
   at MS.Internal.XcpImports.Collection_AddDependencyObject[T](PresentationFrameworkCollection`1 collection, DependencyObject value)
   at System.Windows.PresentationFrameworkCollection`1.AddDependencyObject(DependencyObject value)
   at System.Windows.Controls.UIElementCollection.AddInternal(UIElement value)
   at System.Windows.PresentationFrameworkCollection`1.Add(UIElement value)
   at MTG_Token_Tracker.TokenGraphic.container_Tap(Object sender, GestureEventArgs e)
   at MS.Internal.CoreInvokeHandler.InvokeEventHandler(Int32 typeIndex, Delegate handlerDelegate, Object sender, Object args)
   at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName)

Answer 1

Rather than using UserControls, I would try to use databinding, with ObservableCollection‘s of token classes in the back end. Moving things around becomes a little easier when the GUI part gets taken care of by the binding.

For an example of how to do this, I created a Windows Phone project using the “Windows Phone Pivot Application” template to use as a base, and named it “TokenAnswer” (if you do this and paste in the code below, you should have a working example).

To MainPage.xaml, I added the DoubleTap event to the first list’s item template, and set the SecondListBox binding to “Items2”. I also set Tag={Binding}, which sets the Tag variable to the ItemViewModel behind the GUI item (this is done so I can access the item tapped, there are other ways to do this, but this one is easy enough for this example).

<phone:PhoneApplicationPage 
x:Class="TokenAnswer.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
xmlns:controls="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone.Controls"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
mc:Ignorable="d" d:DesignWidth="480" d:DesignHeight="768" 
d:DataContext="{d:DesignData SampleData/MainViewModelSampleData.xaml}"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}"
SupportedOrientations="Portrait"  Orientation="Portrait"
shell:SystemTray.IsVisible="True">

<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="Transparent">
    <!--Pivot Control-->
    <controls:Pivot Title="MY APPLICATION">
        <!--Pivot item one-->
        <controls:PivotItem Header="first">
            <!--Double line list with text wrapping-->
            <ListBox x:Name="FirstListBox" Margin="0,0,-12,0" ItemsSource="{Binding Items}">
                <ListBox.ItemTemplate>
                    <DataTemplate>
                      <StackPanel DoubleTap="Token_DoubleTap" Tag="{Binding}" Margin="0,0,0,17" Width="432" Height="78">
                          <TextBlock Text="{Binding LineOne}" TextWrapping="Wrap" Style="{StaticResource PhoneTextExtraLargeStyle}"/>
                          <TextBlock Text="{Binding LineTwo}" TextWrapping="Wrap" Margin="12,-6,12,0" Style="{StaticResource PhoneTextSubtleStyle}"/>
                      </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>
        </controls:PivotItem>

        <!--Pivot item two-->
        <controls:PivotItem Header="second"> 
            <!--Triple line list no text wrapping-->
                <ListBox x:Name="SecondListBox" Margin="0,0,-12,0" ItemsSource="{Binding Items2}">
                    <ListBox.ItemTemplate>
                        <DataTemplate>
                            <StackPanel Margin="0,0,0,17">
                                <TextBlock Text="{Binding LineOne}" TextWrapping="NoWrap" Margin="12,0,0,0" Style="{StaticResource PhoneTextExtraLargeStyle}"/>
                                <TextBlock Text="{Binding LineThree}" TextWrapping="NoWrap" Margin="12,-6,0,0" Style="{StaticResource PhoneTextSubtleStyle}"/>
                            </StackPanel>
                        </DataTemplate>
                    </ListBox.ItemTemplate>
                </ListBox>
        </controls:PivotItem>
    </controls:Pivot>
</Grid>

</phone:PhoneApplicationPage>

In the MainViewModel.cs, I added a second collection (“Items2”) and initialized it in the constructor, this collection is for the second listbox:

public MainViewModel()
    {
        this.Items = new ObservableCollection<ItemViewModel>();
        this.Items2 = new ObservableCollection<ItemViewModel>();
    }

    /// <summary>
    /// A collection for ItemViewModel objects.
    /// </summary>
    public ObservableCollection<ItemViewModel> Items { get; private set; }
    public ObservableCollection<ItemViewModel> Items2 { get; private set; }

Finally, in MainPage.xaml.cs, I added the codebehind for the event handler, to remove the item from the first collection, and add it to the second.

private void Token_DoubleTap(object sender, GestureEventArgs e)
    {
        var token = (sender as StackPanel).Tag as ItemViewModel;
        App.ViewModel.Items.Remove(token);
        App.ViewModel.Items2.Add(token);
    }

Hopefully you can use this as a guide to help your current project!