Windows phone Grid Stretch Width in Template selector - windows-phone-7

Question

Hi Everyone this is my first question so, I'll try to be really explicit:
I have a ListBox with a Style and Template to make it a two column style view.
This is the Template for the ListBoxItem:
<DataTemplate x:Key="ItemDataTemplate">
<Grid Height="29">
<Grid.ColumnDefinitions>
<ColumnDefinition Width=".3*" />
<ColumnDefinition Width=".7*" />
</Grid.ColumnDefinitions>
<TextBlock Grid.Column="0" Name="txtBind1" Text="{Binding Codigo}"/>
<TextBlock Grid.Column="1" Name="txtBind2" Text="{Binding Descripcion}"/>
</Grid>
</DataTemplate>
<Style TargetType="ListBoxItem" x:Key="ListboxStretchStyle">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<ContentPresenter HorizontalAlignment="Stretch" VerticalAlignment="Stretch"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="ListBoxStyle" TargetType="ListBox">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<ScrollViewer>
<StackPanel VerticalAlignment="Top">
<Grid Height="30" Background="Gray">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.30*"/>
<ColumnDefinition Width="0.70*" />
</Grid.ColumnDefinitions>
<Border BorderBrush="{StaticResource PhoneBackgroundBrush}" BorderThickness="1">
<TextBlock Grid.Column="0" Text="{Binding CriterioActual.Descripcion}"/>
</Border>
<Border Grid.Column="1" BorderBrush="{StaticResource PhoneBackgroundBrush}" BorderThickness="1">
<TextBlock Grid.Column="1" Text="Descripción"/>
</Border>
</Grid>
<ItemsPresenter/>
</StackPanel>
</ScrollViewer>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
And this is the ListBox:
<ListBox Height="320" Margin="0,84,0,0" Name="ListaArticulos" VerticalAlignment="Top"
Style="{StaticResource ListBoxStyle}"
ItemTemplate="{StaticResource ItemDataTemplate}"
ItemContainerStyle="{StaticResource ListboxStretchStyle}"
ItemsSource="{Binding Articulos}">
</ListBox>
This is the Result:
At this point, everything is fine, so I implemented a TemplateSelector to change the template of the ListBoxItem depending of SelectedItem of a ListBox. So I put the same template into a TemplateSelector but the Grid's Width is not Stretching.
Template Selector:
<DataTemplate x:Key="MultiTemplate">
<Views:ArticulosTemplateSelector Content="{Binding}" Filtro="{Binding ElementName=ComboCriterios, Path=SelectedItem, Mode=OneWay}">
<Views:ArticulosTemplateSelector.FiltroCodigo>
<DataTemplate>
<Grid Height="29" Background="Gray" HorizontalAlignment="Stretch">
<Grid.ColumnDefinitions>
<ColumnDefinition Width=".3*" />
<ColumnDefinition Width=".7*" />
</Grid.ColumnDefinitions>
<TextBlock Grid.Column="0" Name="txtBind1" HorizontalAlignment="Stretch" Text="{Binding Codigo}"/>
<TextBlock Grid.Column="1" Name="txtBind2" HorizontalAlignment="Stretch" Text="{Binding Descripcion}"/>
</Grid>
</DataTemplate>
</Views:ArticulosTemplateSelector.FiltroCodigo>
</DataTemplate>
This is the Updated ListBox:
<ListBox Height="320" Margin="0,84,0,0" Name="ListaArticulos" VerticalAlignment="Top"
Style="{StaticResource ListBoxStyle}"
ItemTemplate="{StaticResource MultiTemplate}"
ItemContainerStyle="{StaticResource ListboxStretchStyle}"
ItemsSource="{Binding Articulos}">
</ListBox>
The Final Result:
The Grid is not stretching, If anyone can please help me I'll apreciate.

Answer 1

The Template Selector has its own Width, so is important to stretch the Selector to allow the Grids to expand its size:
<Views:ArticulosTemplateSelector HorizontalContentAlignment="Stretch" Content="{Binding}" Filtro="{Binding ElementName=ComboCriterios, Path=SelectedItem, Mode=OneWay}">
Note the principal change:
HorizontalContentAlignment="Stretch"
Regards

Answer 2

I got problems with setting Listbox TemplateSelector to span 100%. My solution to this, was to replace Listbox with LongListSelector.