Problem changing template to listview

Hello, I have problems trying to apply different templates to my RadListView on Xamarin Forms.

If I declare my templates as resources on my xaml, i.e.:

<ResourceDictionary>
      <DataTemplate x:Key="templatePortrait" x:Name="templatePortrait">
        <telerikListView:ListViewTemplateCell>
          <telerikListView:ListViewTemplateCell.View>
          <Grid VerticalOptions="FillAndExpand" BackgroundColor="{StaticResource LightGrayBackgroundColor}">
            <Grid.RowDefinitions>
              <RowDefinition Height="50*" />
              <RowDefinition Height="30*" />
              <RowDefinition Height="Auto" />
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
              <ColumnDefinition Width="60*"/>
              <ColumnDefinition Width="40*"/>
            </Grid.ColumnDefinitions>

    </Grid>
        </telerikListView:ListViewTemplateCell.View>
        </telerikListView:ListViewTemplateCell>
      </DataTemplate>

 <DataTemplate x:Key="templateLandscape" x:Name="templatePortrait">
        <telerikListView:ListViewTemplateCell>
          <telerikListView:ListViewTemplateCell.View>
          <Grid VerticalOptions="FillAndExpand" BackgroundColor="{StaticResource LightGrayBackgroundColor}">
            <Grid.ColumnDefinitions>
              <ColumnDefinition Width="50*"/>
              <ColumnDefinition Width="50*"/>
            </Grid.ColumnDefinitions>
    </Grid>
        </telerikListView:ListViewTemplateCell.View>
        </telerikListView:ListViewTemplateCell>
      </DataTemplate>

</ResourceDictionary>

and then I change the item template of my listview when I rotate the device, simply in this way:

listView.ItemTemplate = templateLandscape;

or

listView.ItemTemplate = templatePortrait;

it doesn't work, seems that the new template is not applied.

Instead if I assign the itemtemplate in this way:

listView.ItemTemplate = new DataTemplate(typeof(Templates.TelerikLandscape));

all works as expected. Why?

Where is my mistake?

Thank you