ComboBox in Windows Phone 8.1

Question

Hello , I use Vb2013 Ultimate with emulator Windows Phone 8.1 . If the Items of my ComboBox ( < = 3 items), when you click on it, covering TextBox cannot be selected , because they appear as disabled. if ComboBox is flyout windows, after selecting an item, you don't see it in the box of the ComboBox. I see it only if I click over.

Where am I wrong ?

 

Greetings

Giovanni Pollini

 

 

<!-- Periodicità di capitalizzazione -->
<ComboBox Style="{StaticResource MyComboBox}" Name="EQPERIOV" Grid.Column="1" Grid.Row="2" Width="200" Grid.RowSpan="6" SelectedIndex="0" PlaceholderText="Seleziona Periodicità" SelectedValuePath="Tag" >
<ComboBoxItem Tag="1" Content="Mensile"></ComboBoxItem>
<ComboBoxItem Tag="2" Content="Bimestrale"></ComboBoxItem>
<ComboBoxItem Tag="3" Content="Trimestrale"></ComboBoxItem>
<ComboBoxItem Tag="4" Content="Quadrimestrale"></ComboBoxItem>
<ComboBoxItem Tag="6" Content="Semestrale"></ComboBoxItem>
<ComboBoxItem Tag="12" Content="Annuale"></ComboBoxItem>
</ComboBox>


<!-- ComboBox -->
<Style x:Key="MyComboBox" TargetType="ComboBox">
<Setter Property="Background" Value="White" />
<Setter Property="Foreground" Value="Black" />
<Setter Property="FontFamily" Value="Calibri" />
<Setter Property="FontSize" Value="20" />
<Setter Property="VerticalAlignment" Value="Top" />
<Setter Property="HorizontalAlignment" Value="Right" />
<Setter Property="VerticalContentAlignment" Value="Top" />
<Setter Property="HorizontalContentAlignment" Value="Left" />
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="Height" Value="Auto" />
<Setter Property="Margin" Value="0,0,0,0" />
</Style>