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C# WPF Prism RegionManager failed to navigate

Using WPF .Net Core 3.1 + Prism.
I've implemented TabControl with dynamically added TabItems.
RegionManager works just fine when trying to navigate to region within MainWindow, but it failed when trying to navigate to region whithin the TabPage. Does not work neither from MainWindowViewModel, nor from TabPageViewModel.
Project's repo may be found here: GitHub.
MainWindow.xaml:
<TabControl Margin="10" ItemsSource="{Binding TabPages, UpdateSourceTrigger=PropertyChanged}">
<TabControl.Resources>
<DataTemplate DataType="{x:Type viewmodels:SomeTabPageViewModel}">
<views:SomeTabPage/>
</DataTemplate>
</TabControl.Resources>
<TabControl.ItemTemplate>
<DataTemplate DataType="{x:Type interfaces:ITabPage}" x:Name="dt">
<Grid VerticalAlignment="Stretch" HorizontalAlignment="Stretch" Height="40">
<TextBlock Grid.Column="1" Margin="5,10,10,10" Text="{Binding TabName}" TextAlignment="Center" VerticalAlignment="Center" FontSize="16"/>
</Grid>
</DataTemplate>
</TabControl.ItemTemplate>
</TabControl>
SomeTabPage.xaml:
<UserControl x:Class="WpfPrismRegionFailure.Views.SomeTabPage"
xmlns:prism="http://prismlibrary.com/"
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"
mc:Ignorable="d">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="50"/>
<RowDefinition Height="Auto"/>
<RowDefinition/>
</Grid.RowDefinitions>
<Button Grid.Row="0" Content="Navigate From Inside Of TabPage (not working)" Command="{Binding NavigateFromInsideOfTabPageCommand}" FontSize="16" Background="Orange"/>
<TextBlock Grid.Row="1" Margin="10,20,0,0" Text="The area below contains region 'RegionInsideTabPage', but can't navigate to it." FontSize="16"/>
<Border Grid.Row="2" BorderBrush="Orange" BorderThickness="2" CornerRadius="10" Margin="10">
<ContentControl Margin="10" prism:RegionManager.RegionName="RegionInsideTabPage"/>
</Border>
</Grid>
</UserControl>
SomeTabPageViewModel.cs:
using Prism.Commands;
using Prism.Ioc;
using Prism.Regions;
using System.Windows.Input;
using WpfPrismRegionFailure.Base;
namespace WpfPrismRegionFailure.ViewModels
{
public class SomeTabPageViewModel : TabPageBase
{
public SomeTabPageViewModel(IContainerProvider containerProvider) : base(containerProvider)
{
this.NavigateFromInsideOfTabPageCommand = new DelegateCommand(OnNavigateFromInsideOfTabPage);
}
public SomeTabPageViewModel(IRegionManager regionManager) : base (regionManager)
{
this.NavigateFromInsideOfTabPageCommand = new DelegateCommand(OnNavigateFromInsideOfTabPage);
}
public ICommand NavigateFromInsideOfTabPageCommand { get; }
private void OnNavigateFromInsideOfTabPage()
{
System.Diagnostics.Trace.WriteLine($"SomeTabPageViewModel _regionManager ContainsRegionWithName RegionInsideTabPage: {this._regionManager.Regions.ContainsRegionWithName("RegionInsideTabPage")}");
this._regionManager.RequestNavigate("RegionInsideTabPage", "RegionContent");
}
}
}
Inside of TabPageViewModel regionManager.Regions.ContainsRegionWithName("RegionInsideTabPage") returns 'false' despite of the region is being declared in XAML
<ContentControl Margin="10" prism:RegionManager.RegionName="RegionInsideTabPage"/>
Project's repo may be found here: GitHub.
Someone heeeeeeelp me please

Changing size of User Control

I'm having a problem with determining which element is responsible for a size misalignment. Here is a picture to illustrate it: click here to see it
The light grey area is the element size which I am trying to change, but cannot. The overall area is a User Control, the area inside the Tab is a WPF (as an element Host). I've tried changing both, but with no effect on the grey area (the other tabs are also affected by this). Here is the code for the hosted element (WPF):
<UserControl x:Class="SlideAnalyzer.DisplayAnalysis"
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:SlideAnalyzer"
mc:Ignorable="d"
d:DesignHeight="150.8" d:DesignWidth="201.2">
<Grid Name="displayGrid" Height="64" VerticalAlignment="Bottom" HorizontalAlignment="Center" Width="160" Margin="10,0,31.6,9.4" RenderTransformOrigin="0.496,0.94">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Expander x:Name="expander" Grid.Row="0" Header="Titel zu lang" HorizontalAlignment="Left" VerticalAlignment="Top" Width="180" Background="Red" Margin="-10,-56,0,0">
<Grid Background="AliceBlue">
<TextBlock TextWrapping="Wrap"
Margin="5"><Run Text="This is some text content."/></TextBlock>
</Grid>
</Expander>
</Grid>
The host itself is a normal User Control. I cannot seem to get the right size of the hosted element so that the preview really reflects reality (because when I run the Add-In, the size of the WPF differs)
I tried changing the Properties of the UserControl and I found that AutoSize has a big impact when True (by default False)
Thanks!

WPF Recursive User Control

I have created a User Control that is designed to simplify the use of a recursive popup dialog system in which a popup dialog can have a popup dialog open within it.
Here is the User Control's XAML:
<UserControl x:Class="SEA.WPF.View.Controls.DialogPresenter"
Name="This"
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:SEA.WPF.View.Controls"
xmlns:ts="clr-namespace:SEA.WPF.View.TemplateSelectors"
xmlns:c="clr-namespace:SEA.WPF.View.DataConverters"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300">
<UserControl.Resources>
<ResourceDictionary>
<c:InstanceToVisibilityConverter x:Key="InstanceToVisibilityConverter" />
</ResourceDictionary>
</UserControl.Resources>
<Grid Visibility="{Binding Dialog, Converter={StaticResource InstanceToVisibilityConverter}}">
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition Height="Auto" />
<RowDefinition />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition Width="Auto" />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Border Grid.Row="1" Grid.Column="1">
<ContentControl Content="{Binding Path=Dialog, ElementName=This}"
ContentTemplateSelector="{Binding Path=DialogTemplateSelector, ElementName=This}" />
</Border>
<ContentControl Grid.RowSpan="3" Grid.ColumnSpan="3" Content="{Binding Path=Dialog.Dialog, ElementName=This}">
<ContentControl.ContentTemplateSelector>
<ts:InstanceOnlyTemplateSelector>
<ts:InstanceOnlyTemplateSelector.Template>
<DataTemplate>
<local:DialogPresenter Dialog="{Binding Path=Dialog.Dialog, ElementName=This}"
DialogTemplateSelector="{Binding Path=DialogTemplateSelector, ElementName=This}" />
</DataTemplate>
</ts:InstanceOnlyTemplateSelector.Template>
</ts:InstanceOnlyTemplateSelector>
</ContentControl.ContentTemplateSelector>
</ContentControl>
</Grid>
</UserControl>
Here is InstanceOnlyTemplateSelector:
using System.Windows;
using System.Windows.Controls;
namespace SEA.WPF.View.TemplateSelectors
{
public class InstanceOnlyTemplateSelector : DataTemplateSelector
{
public DataTemplate Template
{
get;
set;
}
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
return item == null ? null : Template;
}
}
}
The InstaceOnlyTemplateSelector is there so that the recursive DialogPresenter is only rendered when the child dialog is not null (thus avoiding a Stack Overflow cause by the recursive binding).
The problem is, that when the child dialog changes from null to something else then the recursive DialogPresenter does not render like it's parent. I have tried replacing the DialogPresenter with a Grid with Background equal to Brushes.Black and that made the whole screen black (as expected).
Why is the recursive instance of the DialogPresenter not rendering as expected?

set deledate in ItemsControl ResourceDictionary

First, let me show you how my code is cut.
I have this code in a xaml UC (eventsUC.xaml) :
<UserControl x:Class="QuimeO.UserControls.Lists.EventsListUC"
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:ToggleSwitch="clr-namespace:ToggleSwitch;assembly=ToggleSwitch"
mc:Ignorable="d"
Width="477"
>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<ScrollViewer HorizontalScrollBarVisibility="Disabled" Width="auto" VerticalScrollBarVisibility="Auto" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
<ItemsControl Grid.Row="0" BorderThickness="0" x:Name="eventsList" ScrollViewer.VerticalScrollBarVisibility="Auto" HorizontalContentAlignment="Stretch" ScrollViewer.HorizontalScrollBarVisibility="Disabled">
<ItemsControl.Resources>
<ResourceDictionary x:Name="eventslisttempplate" Source="EventsListTemplate.xaml" />
</ItemsControl.Resources>
</ItemsControl>
</ScrollViewer>...
My EventsListTemplate.xaml looks like this :
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="QuimeO.UserControls.Lists.EventsListTemplate"
xmlns:apiNamespace="clr-namespace:QuimeO.DBO"
>
<DataTemplate DataType="{x:Type apiNamespace:EventsDictionary}">
<StackPanel Orientation="Vertical">
<Border BorderBrush="LightGray" BorderThickness="0,0,0,1" Margin="0,5,0,0">
<TextBlock HorizontalAlignment="Right" Foreground="Gray" Text="{Binding FormatedDate}" FontSize="14"></TextBlock>
</Border>
<ListView Grid.Row="0" x:Name="eventsList" ItemsSource="{Binding Events}" BorderThickness="0" MouseDoubleClick="eventsList_MouseDoubleClick">
</ListView>
</StackPanel>
</DataTemplate>
</ResourceDictionary>
And my EventsListTemplate.xaml.cs code behind looks like this
public partial class EventsListTemplate : ResourceDictionary
{
public Delegate MainWindowControlPointer;
private void eventsList_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
var ev = ((sender as ListView).SelectedItem as ListViewItem).DataContext as Event;
System.Diagnostics.Debug.WriteLine(ev.Name);
this.MainWindowControlPointer.DynamicInvoke(ev.Ancestors.Root, new Element() { Category = ev.Category, Id = ev.Id, Name = ev.Name });
}
}
When I click on an item of my listview in my template, it trigger the eventsList_MouseDoubleCkick and I can retrieve my event.
However, I would like to trigger an action in the UC where the template is created (first source code block).
To do that, I just want to create a delegate in my Template (technicaly, in a perfect world, something like "this.rd_eventslisttemplate.MainWindowControlPointer = ... "). But, I don't know how to do it or if this is even possible.

After encrypting your question for a while I think I got it.
There is a nice method called VisualTreeHelper.GetParent() which gets you the parent of a control in VisualTree.
Now to your problem when you catch your event in EventsListTemplate you will need to call GetParent() few times till you finally get the instance of your UserControl.
Thats it.

how do i get my datagrid to grow with the window and maintain margins?

Everything about my layout will flow with the resizing of the main window. The problem I'm facing is that as you can see, the datagrid goes off the screen. If you maximize the window, the datagrid will resize with the window, but continue to go off the screen. How do I get it to maintain its margin of 20 with it's parent grid?
<Grid>
<StackPanel Orientation="Vertical">
<TextBox Height="170" Name="txtSQL" VerticalAlignment="Top" AcceptsReturn="True" TextWrapping="Wrap" Margin="20"/>
<Button Content="Run!" Height="23" HorizontalAlignment="Left" Name="btnRun" VerticalAlignment="Top" Margin="20,0,0,0" Width="75" Click="btnRun_Click" />
<Grid>
<my:DataGrid Name="dgResults" VerticalAlignment="Top" Margin="20" />
</Grid>
</StackPanel>
</Grid>
UPDATE:
Just to be more specific. The effect I'm trying to accomplish here is this:
When the window first loads, you are presented with a blank datagrid, so it's only about 15 pixels high. When you run the query, it will populate the datagrid by reassigning the itemssource. As of now, when you do that, if the data exceeds the window size, it will go off the bottom of the screen. I need it to only expand to the bottom of the window then enable the scrollbar. I can do this just by wrapping it in a scrollviewer im sure. However, when the window is resized, the datagrid needs to resize with it.
I'm wondering if the setup might have something to do with it. The form is actually a wpf page being displayed in a frame.
UPDATE:
<Page x:Class="Hold_Database___Prototype_1.Views.SQL"
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"
mc:Ignorable="d"
d:DesignHeight="304" d:DesignWidth="732"
Title="SQL" xmlns:my="http://schemas.microsoft.com/wpf/2008/toolkit" AllowDrop="True">
<Grid>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition Height="23" />
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBox Height="170" Name="txtSQL" VerticalAlignment="Top" AcceptsReturn="True" TextWrapping="Wrap" Margin="20" Grid.Row="0"/>
<Button Content="Run!" Height="23" HorizontalAlignment="Left" Name="btnRun" VerticalAlignment="Top"
Margin="20,0,0,0" Width="75" Grid.Row="1" Click="btnRun_Click" />
<DockPanel Grid.Row="2">
<my:DataGrid Name="dgResults" Margin="20" />
</DockPanel>
</Grid>
</Page>

What is the dock panel for in this example?
Try putting the DataGrid directly in the cell with no stackpanel. If you are setting the button height then set set grid to auto.
Also, why give so much space to the text?
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBox Height="170" Name="txtSQL" VerticalAlignment="Top" AcceptsReturn="True" TextWrapping="Wrap" Margin="20" Grid.Row="0"/>
<Button Content="Run!" Height="23" HorizontalAlignment="Left" Name="btnRun" VerticalAlignment="Top"
Margin="20,0,0,0" Width="75" Grid.Row="1" Click="btnRun_Click" />
<my:DataGrid Grid.Row="2" <my:DataGrid Name="dgResults" Margin="20" />
Then also set HorizontalAlignment, VerticleAlignment, HorizontalContentAlignment, and VerticalContentAlignment = stretch

Your Grid is drawn off screen without a scroll bar because you are using a StackPanel. Care must be taken when using StackPanel - it is the most simplistic of all WPF Panel derived classes since its MeasureOverride calls Measure for all of its children with a size of double.PositiveInifity regardless of how much space the panel actually has available. Even a ScrollViewer will not help you with a StackPanel (the ScrollBar will be shown, but you won't be able to move it).
For example, consider a Window 350 in height and width, and a single Button as its content which is 500 in both height and width:
<Window x:Class="WpfApplication2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="350">
<StackPanel>
<ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
<Button Content="Hello" Height="500" Width="500" />
</ScrollViewer>
</StackPanel>
</Window>
Similar to your example, the Button here is drawn off screen in both the vertical and horizontal directions and a non-functional scroll bar will be present. If we change the panel to one which respects the size of its given area (e.g. DockPanel):
<Window x:Class="WpfApplication2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<DockPanel>
<ScrollViewer>
<Button Content="Hello" Height="500" />
</ScrollViewer>
</DockPanel>
</Window>
then scroll bars appear which are functional and hence allow the content off screen to be shown by scrolling.
Hope this helps!

What I have done was do define the horizontal and vertical alignments to "Stretch" respectively at the control you want (your DataGrid) to take up the size based on the window being resized.