Set ContentDialog to show on bottom of page in UWP - xaml

Question

I have several ContentDialogs in a RelativeLayout and want them to appear or have the the vertical alignment to "bottom". But it seems that no matter what I try the dialogs always appear on the top of the screen.
This is how they look now
Any ideas?
Here is a xaml code snippet:
<RelativePanel Height="{Binding ActualHeight, ElementName=Page}" >
<ContentDialog x:Name="EntrepriseDialog"
VerticalAlignment="Bottom"
Title="Vælg entreprise"
PrimaryButtonText=""
IsPrimaryButtonEnabled="{Binding IsChecked, ElementName=checkBoxAgree, Mode=OneWay}"
MaxWidth="{Binding ActualWidth, ElementName=pageRoot}" Grid.ColumnSpan="2" Margin="30,194,-71,-194">
<ListView Name="ListEntreprises" VerticalAlignment="Bottom" SelectionChanged="ListEntreprises_SelectionChanged">
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<Setter Property="HorizontalContentAlignment" Value="Stretch"></Setter>
<Setter Property="Margin" Value="0,0,0,1"></Setter>
<Setter Property="Background" Value="Transparent"></Setter>
<Setter Property="Padding" Value="5"></Setter>
</Style>
</ListView.ItemContainerStyle>
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<StackPanel>
<TextBlock>
<Run FontSize="15" Text="{Binding Name}"/>
</TextBlock>
<TextBlock Visibility="Collapsed">
<Run Text="{Binding Id}"/>
</TextBlock>
</StackPanel>
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ContentDialog>
<ContentDialog x:Name="SaveChooseDialog"
VerticalAlignment="Bottom"
Title=""
PrimaryButtonText=""
IsPrimaryButtonEnabled="{Binding IsChecked, ElementName=checkBoxAgree, Mode=OneWay}"
MaxWidth="{Binding ActualWidth, ElementName=pageRoot}" Grid.ColumnSpan="2" Margin="30,148,-71,-148">
<ListBox Name="ListBoxSaveMode" SelectionChanged="ListBoxSaveMode_SelectionChanged">
<ListBoxItem>
<TextBlock Name="TxtLocally" Text="Gem lokalt"/>
</ListBoxItem>
<ListBoxItem>
<TextBlock Name="TxtServer" Text="Gem på server"/>
</ListBoxItem>
<ListBoxItem>
<TextBlock Name="TxtCancel" Text="Annullér"/>
</ListBoxItem>
</ListBox>
</ContentDialog>
<ContentDialog x:Name="AddPictureDialog"
VerticalAlignment="Bottom"
Title=""
PrimaryButtonText=""
IsPrimaryButtonEnabled="{Binding IsChecked, ElementName=checkBoxAgree, Mode=OneWay}"
MaxWidth="{Binding ActualWidth, ElementName=pageRoot}" Grid.ColumnSpan="2" Margin="30,142,-71,-142">
<ListBox Name="ListBoxAddPicture" SelectionChanged="ListBoxAddPicture_SelectionChanged">
<ListBoxItem>
<TextBlock Name="TxtFromCamera" Text="Tag et nyt"/>
</ListBoxItem>
<ListBoxItem>
<TextBlock Name="TxtFromStorage" Text="Vælg fra kamerarulle"/>
</ListBoxItem>
</ListBox>
</ContentDialog>
</RelativePanel>
EDIT: XAML for entire Page
<Page
Name="Page"
x:Class="...Pages.Documentation.DocumentationCreatePage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:...Pages.Documentation"
xmlns:userControl="using:...Pages.Controls"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Background="#8FBC3E">
<Grid>
<Grid.Background>
<ImageBrush Stretch="UniformToFill" ImageSource="/Assets/Images/mainBg.png" />
</Grid.Background>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<StackPanel>
<Grid Height="40" Background="#8FBC3E" >
<StackPanel Orientation="Horizontal">
<Button Name="BtnBack" Click="BtnBack_Click" Margin="20 0 20 0" >
<Button.Template>
<ControlTemplate>
<TextBlock FontSize="20" Foreground="White" FontFamily="Segoe MDL2 Assets" Text=""></TextBlock>
</ControlTemplate>
</Button.Template>
</Button>
<TextBlock Name="TxtTitle" VerticalAlignment="Center" HorizontalAlignment="Center" Foreground="White" FontSize="18"/>
</StackPanel>
</Grid>
<userControl:SyncDataControl></userControl:SyncDataControl>
</StackPanel>
<Grid Grid.Row="1" Name="StackPanel">
<ProgressRing Name="SaveProgressRing" IsActive="False" Foreground="#8FBC3E" Width="40" Height="40" Margin="152,239,87,321" />
<StackPanel Grid.ColumnSpan="2" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
<ListView Name="ListViewDocumentationItems" ScrollViewer.VerticalScrollMode="Disabled" SelectionChanged="ListViewDocumentationItems_SelectionChanged">
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<Setter Property="Height" Value="80"></Setter>
<Setter Property="HorizontalContentAlignment" Value="Stretch"></Setter>
<Setter Property="VerticalContentAlignment" Value="Center"></Setter>
<Setter Property="Margin" Value="0,0,0,1"></Setter>
<Setter Property="Background" Value="White"></Setter>
</Style>
</ListView.ItemContainerStyle>
<ListView.ItemTemplate>
<DataTemplate>
<Grid VerticalAlignment="Center">
<StackPanel Padding="0 0 10 0" Orientation="Horizontal" >
<Image Source="{Binding ImageSource}" VerticalAlignment="Center" Height="40" Margin="5 0 5 0"></Image>
<TextBlock Foreground="Black" HorizontalAlignment="Left" VerticalAlignment="Center">
<Run FontWeight="Bold" FontSize="20" Text="{Binding Name}"/>
</TextBlock>
</StackPanel>
<Grid HorizontalAlignment="Right">
<StackPanel Orientation="Horizontal">
<TextBlock Foreground="Black" VerticalAlignment="Center" Padding="0 0 20 0">
<Run FontSize="15" Text="{Binding Count}"/>
</TextBlock>
<Image Width="15" Height="15" VerticalAlignment="Center" Source="/Assets/Images/rightarrow.png" />
</StackPanel>
</Grid>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<TextBlock Name="TxtDocDesc" TextWrapping="Wrap" Foreground="Gray" Height="53" />
<ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
<StackPanel Name="PicturePanel" Orientation="Horizontal" Margin="15 0 15 0" />
</ScrollViewer>
</StackPanel>
<Button Name="BtnSave" Grid.Row="2" VerticalAlignment="Bottom" FontSize="25" Click="BtnSave_Click" Background="#8FBC3E" Foreground="White" Height="60" Content="Gem" HorizontalAlignment="Stretch" Margin="5 5 5 5"/>
<RelativePanel VerticalAlignment="Stretch" >
<ContentDialog x:Name="EntrepriseDialog" VerticalContentAlignment="Bottom"
RelativePanel.AlignBottomWithPanel="True"
Title="Vælg entreprise"
PrimaryButtonText=""
IsPrimaryButtonEnabled="{Binding IsChecked, ElementName=checkBoxAgree, Mode=OneWay}"
MaxWidth="{Binding ActualWidth, ElementName=pageRoot}" >
<ListView Name="ListEntreprises" VerticalAlignment="Bottom" SelectionChanged="ListEntreprises_SelectionChanged">
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<Setter Property="HorizontalContentAlignment" Value="Stretch"></Setter>
<Setter Property="Margin" Value="0,0,0,1"></Setter>
<Setter Property="Background" Value="Transparent"></Setter>
<Setter Property="Padding" Value="5"></Setter>
</Style>
</ListView.ItemContainerStyle>
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<StackPanel>
<TextBlock>
<Run FontSize="15" Text="{Binding Name}"/>
</TextBlock>
<TextBlock Visibility="Collapsed">
<Run Text="{Binding Id}"/>
</TextBlock>
</StackPanel>
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ContentDialog>
<ContentDialog x:Name="SaveChooseDialog"
RelativePanel.AlignBottomWithPanel="True"
Title=""
PrimaryButtonText=""
IsPrimaryButtonEnabled="{Binding IsChecked, ElementName=checkBoxAgree, Mode=OneWay}"
MaxWidth="{Binding ActualWidth, ElementName=pageRoot}">
<ListBox Name="ListBoxSaveMode" SelectionChanged="ListBoxSaveMode_SelectionChanged">
<ListBoxItem>
<TextBlock Name="TxtLocally" Text="Gem lokalt"/>
</ListBoxItem>
<ListBoxItem>
<TextBlock Name="TxtServer" Text="Gem på server"/>
</ListBoxItem>
<ListBoxItem>
<TextBlock Name="TxtCancel" Text="Annullér"/>
</ListBoxItem>
</ListBox>
</ContentDialog>
<ContentDialog x:Name="AddPictureDialog"
Title=""
PrimaryButtonText=""
IsPrimaryButtonEnabled="{Binding IsChecked, ElementName=checkBoxAgree, Mode=OneWay}"
MaxWidth="{Binding ActualWidth, ElementName=pageRoot}" >
<ListBox Name="ListBoxAddPicture" SelectionChanged="ListBoxAddPicture_SelectionChanged">
<ListBoxItem>
<TextBlock Name="TxtFromCamera" Text="Tag et nyt"/>
</ListBoxItem>
<ListBoxItem>
<TextBlock Name="TxtFromStorage" Text="Vælg fra kamerarulle"/>
</ListBoxItem>
</ListBox>
</ContentDialog>
<ContentDialog x:Name="DialogDownloadProgress"
VerticalAlignment="Stretch"
Title=""
MaxWidth="{Binding ActualWidth, ElementName=pageRoot}">
<StackPanel Padding="0,50">
<TextBlock Name="ProgressTitle" Text="Test test" HorizontalAlignment="Center" Padding="0 0 0 20"/>
<ProgressBar x:Name="ProgressBarDownload" HorizontalAlignment="Stretch" IsEnabled="True"></ProgressBar>
</StackPanel>
</ContentDialog>
</RelativePanel>
</Grid>
</Grid>

Answer 1

It seems the positioning of ContentDialog instances is not in the hands of the developer, at least not without custom versions of it. Afaik the OS will decide where to place the dialog for you.
See here for more information:
http://www.reflectionit.nl/blog/2015/windows-10-xaml-tips-messagedialog-and-contentdialog
So if positioning of the dialog is critical then you might have to create a custom control.