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UWP - Pass event to control (tunneling)

I have a UWP question about inheriting/ passing a event to a user control from the parent view to child.
I created a user control to display text overlays (see code below). We had a parent view that would display an overlay when the window is resized (see code below). The overlay would display the dimensions of the window when this even is triggered.
I moved the overlay to a user control and now I'm trying to pass that resized event to the overlay control. The hope is that we can register more events to the overlay control so it can display more then the resize
information. However, I'm not sure the best way to do this. My first idea was inheriting from the view, so i could just listen to the event from the overlay control, but that resulted in errors.
I believe due to the fact that the parent view has a ViewModel (i also created one for the overlay, not sure if its actually needed yet).
I have been reading about a lot of possible ways to do this, but I'm not sure which would be the best way to do this. Does anyone have any insight on this issue ? I would be open to suggestions, links, or just a general answer of
what is the best way to achieve this in our project.
Parent view
User Control
Parent Event
Control class
Some information i have been reading about:
https://documentation.devexpress.com/WPF/17449/MVVM-Framework/ViewModels/ViewModel-relationships-ISupportParentViewModel
https://learn.microsoft.com/en-us/dotnet/framework/wpf/advanced/preview-events
https://social.msdn.microsoft.com/Forums/windows/en-US/742077f6-e875-44d1-8bc4-6e6516db9eda/passing-the-parent-control-event-to-child-controls?forum=winforms
https://learn.microsoft.com/en-us/windows/uwp/xaml-platform/events-and-routed-events-overview
http://irisclasson.com/2013/12/10/passing-event-arguments-from-xaml-in-windows-store-apps-inputconverter-inputconverterparameter-etc/
https://learn.microsoft.com/en-us/windows/uwp/launch-resume/how-to-create-and-consume-an-app-service
Update
Adding the viewModel to the parent viewModel (terminal), and passing it to the control via the Datacontext did not work

As you're already using MVVM, I'd recommend going the full route utilizing "Interactivity", "Commands", and "child ViewModels". This is a commonly used patter in MVVM WPF applications, and can be applied to UWP apps as well.
Using "Interactivity" and interactions
The interactivity / behaviors library from Microsoft allows you to bind events in XAML to an ICommand in the ViewModel. You can get the managed NuGet package here.
From the official examples on GitHub, shortened:
<Button x:Name="button1" Content="Increment">
<Interactivity:Interaction.Behaviors>
<Interactions:EventTriggerBehavior EventName="Click" SourceObject="{Binding ElementName=button1}">
<Interactions:InvokeCommandAction Command="{Binding UpdateCountCommand}"/>
</Interactions:EventTriggerBehavior>
</Interactivity:Interaction.Behaviors>
</Button>
Forward command data to child ViewModel
Having this event now routed to your command in your parent ViewModel, you can now either call your overlay ViewModel and pass the info directly to it:
private readony IOverlayViewModel _overlayViewModel;
public ICommand UpdateCountCommand { get; set; }
ctor(IOverlayViewModel overlayViewModel)
{
_overlayViewModel = overlayViewModel;
UpdatedCountCommand = new MyICommandImplementation(UpdatedCountCommand_Executed);
}
private void UpdatedCountCommand_Executed(/* Add correct method signature */)
{
// If needed, retrieve data from parameter...
// Update overlay ViewModel text
_overlayViewModel.Text = ""; // Whichever text was calculated before
}
Or you use a messenger (mediator pattern) to send it to an overlay.

I was misusing the bindings. x:Bind and Binding are using different types of context. For this binding to work we would need to set the parent's element Datacontext to 'this'. x:Bind on the other hand does this implicitly.
<views:OverlayView DataContext="{x:Bind ViewModel.Overlay}"></views:OverlayView>

C# WPF userControl to send data to mainWindow textBlock on buttonClick

I am trying to create a simple onscreen keypad created using buttons (currently a User-control), on those buttons i have a click event, when i click/touch a button i want the value of that button sent to a Text-block in my Main-window.
I can't/don't understand how to make the User-control (keypad) see the Text-block (in Main-window) to add in the value that i need.
I have seen solutions that use command Bindings and solutions that use the visual tree traversing but all of them are the main window accessing the user control, not the other way around.

All the examples are the other way around because that is how a UserControl is supposed to work.
A UserControl is a packaged piece of re-usable functionality. It should not know anything about the code that is using it.
Instead you should expose routed events in your UserControl for things like a when number was selected, and subscribe to them in your main window.

There are many ways to achieve what you want. If your MainWindow.xaml has a UserControl and you want to react to a change from the control in the MainWindow.xaml.cs file, then you could add a delegate to the UserControl code behind and register a handler for it in the MainWindow.xaml.cs file. Implementing new delegates are generally somewhat simpler than implementing RoutedEvents, which is another way that you could handle this situation.
Using a delegate like this will enable you to effectively pass a signal to the main view from the child UserControl code behind, which you can react to in any way you want to. Rather than explain the whole story again here, please see my answers from the Passing parameters between viewmodels and How to call functions in a main view model from other view models? posts here on Stack Overflow for full details on how to achieve this.

Event Handler located in different class than MainWindow

So I followed the guide on the following site to restrict the characters a textbox can accept.
http://www.rhyous.com/2010/06/18/how-to-limit-or-prevent-characters-in-a-textbox-in-csharp/
My problem is I can't figure out how to make the event handler trigger in the secondary class. Basically how do I tell VS to look for the event handler code in that class instead of MainWindow? I tried searching, but apparently don't know the correct terms to use. The xaml reference I used was
xmlns:DigitBox="clr-namespace:System.Windows.Controls;assembly=PresentationFramework"
Any ideas?

Simplest way I've found to do it is assign the event in your constructor.
public MainWindow()
{
InitializeComponent();
TextBoxCurrency.GotFocus += expandedTextBoxEvents.TextBoxCurrencyGotFocus;
TextBoxCurrency.LostFocus += expandedTextBoxEvents.TextBoxCurrencyLostFocus;
}
I've searched a way to do it in XAML and I did not found an easy and clean way to do it.

You are much better off using commands and command bindings. I'm not sure what the specific command that would would bind to for a text box for your desired functionality, but one of the goals for WPF was to lessen the use of Event Handlers in code behind.
Check out this article for an overview of commands and this article for a way to hook up commands with events. WPF commanding is one of the coolest features to enable true separation of concerns between UI and business logic.
As a worst case scenario solution, you could create your own text box that inherits from the text box control and hook up the events in that class. Your control would then be reusable.

UserControl event implementation on parent

I am converting a Delphi 7.0 application to .Net(2.0).
In Delphi application there is similar implementation like "User Control", So I too did same in my C# application.
But in Delphi it is possible to code UserControl's events implemantations on main(parent), unlikely in .Net it is a must(not sure) to do it at UserControl level.
My Questions are,
Can't we do same in .Net?
Altenative method(direct) method of doing that
Note: I have achived what I want through delegates/events, But I prefer the way done it in Delphi

You can couple of alternate ways to achieve this:
Make controls members (generated by designer) within user controls as public or internal (possible by setting Modifiers property in control properties). Then you can write code such as UserCtr1.UserCtr2.UserCtrl3.Btn1 to reference the button and attach event handler to it within form code. I won't prefer this approach because it breaks the encapsulation. But if your taking view that user controls are just a UI template (w/o any behavior) then it may work out for you.
Yet another way would be to have local event handlers within control code but make them invoke corresponding methods from Form. This can be accomplished by using TopLevelControl property. For example, in User Ctrl 3 code
private void Btn1_Click(object sender, EventArgs e)
{
((FormMain)this.TopLevelControl).Search(param1);
}
Problem with this approach is tight coupling with form and way to resolve would be to inject some interface to invoke functions from user control. Form can implement the interface. The instance (of interface) can be injected to all user controls via some kind of IoC Container/DI framework.

How to pass information from one WPF UserControl to another WPF UserControl?

I've got a WPF application.
On the left side there is a stackpanel full of buttons.
On the right side there is an empty dockpanel.
When user clicks a button, it loads the corresponding UserControl (View) into the dockpanel:
private void btnGeneralClick(object sender, System.Windows.RoutedEventArgs e)
{
PanelMainContent.Children.Clear();
Button button = (Button)e.OriginalSource;
Type type = this.GetType();
Assembly assembly = type.Assembly;
IBaseView userControl = UserControls[button.Tag.ToString()] as IBaseView;
userControl.SetDataContext();
PanelMainContent.Children.Add(userControl as UserControl);
}
This pattern works well since each UserControl is a View which has a ViewModel class which feeds it information which it gets from the Model, so the user can click from page to page and each page can carry out isolated functionality, such as editing all customers, saving to the database, etc.
Problem:
However, now, on one of these pages I want to have a ListBox with a list of Customers in it, and each customer has an "edit" button, and when that edit button is clicked, I want to fill the DockPanel with the EditSingleCustomer UserControl and pass it the Customer that it needs to edit.
I can load the EditCustomer usercontrol, but how do I pass it the customer to edit and set up its DataContext to edit that customer?
I can't pass it in the constructor since all the UserControls are already created and exist in a Dictionary in the MainWindow.xaml.cs.
so I created a PrepareUserControl method on each UserControl and pass the Customer to it and can display it with a textbox from code behind with x:Name="..." but that is not the point, I need to DataBind an ItemsControl to a ObservableCollection to take advantage of WPF's databinding functionality of course.
so I tried to bind the ListBox ItemSource in the View to its code behind like this:
<UserControl.Resources>
<local:ManageSingleCustomer x:Key="CustomersDataProvider"/>
</UserControl.Resources>
<DockPanel>
<ListBox ItemsSource="{Binding Path=CurrentCustomersBeingEdited, Source={StaticResource CustomersDataProvider}}"
ItemTemplate="{DynamicResource allCustomersDataTemplate}"
Style="{DynamicResource allCustomersListBox}">
</ListBox>
</DockPanel>
which gets a stackoverflow error caused by an endless loop in the IntializeComponent() in that view. So I'm thinking I'm going about this in the wrong way, there must be some easier paradigm to simply pass commands from one UserControl to another UserControl in WPF (and before someone says "use WPF commanding", I already am using commanding on my UserControl that allows the user to edit all customers, which works fine, but I have to handle it in my code behind of my view (instead of in my viewmodel) since I need the parent window context to be able to load another user control when its finished saving:
<Button Style="{StaticResource formButton}"
Content="Save"
Command="local:Commands.SaveCustomer"
CommandParameter="{Binding}"/>
private void OnSave(object sender, System.Windows.Input.ExecutedRoutedEventArgs e)
{
Customer customer = e.Parameter as Customer;
Customer.Save(customer);
MainWindow parentShell = Window.GetWindow(this) as MainWindow;
Button btnCustomers = parentShell.FindName("btnCustomers") as Button;
btnCustomers.RaiseEvent(new RoutedEventArgs(Button.ClickEvent));
}
So how in WPF can I simply have a UserControl loaded in a DockPanel, inside that UserControl a button with a command on it that loads another UserControl and sends that UserControl a specific object to which it can bind its controls?
I can imagine I just do not know enough about WPF commands at this point, if anyone can point me in the right direction from here, that would be great, or if you think this "loading UserControls in a DockPanel pattern is foreign to WPF and should be avoided and replaced with another way to structure applications", that would be helpful news as well. You can download the current state of my application here to get an idea of how it is structured. Thanks.

I've just finished a LOB application using WPF where this sort of problem/pattern appeared constantly, so here's how I would have solved your problem:
1) In the DataTemplate where you create each item in the ListBox, along with it's edit button, bind the Button's tag property to the Customer object underlying that list box item.
2) Create a Click event handler for the button, and set the Button's Click event to fire the handler.
3) In the event handler, set the Content property of the UserControl.
4) Set up a DataTemplate in scope of the User Control (perhaps in the resources of it's immediate container) which describes an editor for that single customer.
Another approach that will work is to declare a Customer dependency property on your EditCustomer class, then set that property (perhaps through a XAML Trigger) when the button is clicked.
I hope this isn't too vague. If nothing else, know that the problem you're facing is very solvable in WPF.

This is where you use the Mediator pattern. There's several blog posts on this topic (for instance), and there's implementations of the pattern in some WPF frameworks (such as EventAggregator in Prism).

I don't have the time to really dig into this (it's an interesting question and I hope you get a good answer-- I can see myself running into a similar situation in the future).
Have you considered getting a little less WPF-y and falling back to firing an event on your source UserControl with an EventArgs that contains the customer, then in the event handler, firing the appropriate command on the target control?