Tour_Dueva/AddEditPage.xaml

<Page x:Class="DuevaTours.AddEditPage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:local="clr-namespace:DuevaTours"
      mc:Ignorable="d" 
      d:DesignHeight="450" d:DesignWidth="800"
      Title="AddEditPage">

    <Grid>
        <TextBlock Text="Hello!" HorizontalAlignment="Center" VerticalAlignment="Center" FontSize=" 30"></TextBlock>
    </Grid>
</Page>