Silverlight Set IE Full Screen

public partial class Page : UserControl

    {

        public Page()

        {

            InitializeComponent();

        }

        private void Button_Click(object sender, RoutedEventArgs e)

        {

            ToggleFullScreen();

        }

        private void ToggleFullScreen()

        {

            Application.Current.Host.Content.IsFullScreen = !Application.Current.Host.Content.IsFullScreen;

        }

    }

How to sort combind field in datagrid.

I use the code below to combine

<sdk:DataGridTemplateColumn Header="MergeColumn" Width="90">
<sdk:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" Margin="3,4,0,0">
<TextBlock Text="{Binding FieldA}" />
<TextBlock Text="{Binding FieldB}" />
</StackPanel>
</DataTemplate>
</sdk:DataGridTemplateColumn.CellTemplate>
</sdk:DataGridTemplateColumn>

Xap packaging failed. Object reference not set to an instance of an object

I'm getting this error message on my PC when I try to build  Silverlight App:

Xap packaging failed. Object reference not set to an instance of an object 

I'm using Dropbox. On my laptop, It works perfectly fine and I can debug etc...

Please tried many things such as:

• Delete obj/Debug Folder
• Check for files which are missing on the Solution Explorer