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It seems Xamarin ListView binding is broken in updated VS 2019 16.11.3. CollectionView binding too. Can Someone look into it?

I wasted 2 days to figure out whats the issue but I couldnt. I tried all the possible examples, source codes from Github, tutorials, articles etc. I could not bind the List and its contents to a ListView or CollectionView.
Visual studio Version 16.11.3
Xamarin Version
My ViewModel. I tried using list and observable collection.
My CodebehindFile. I tried Binding from Xaml as well as from code behind file.
my Xaml file. I spent 2 days figuring out this Binding issue :(
A simple class in the model.
I wrote a new page which works with basic declaration of ListView contents but...,
I have copied the working code on to the Main page but its not working on the MainPage. The listView which works fine on the other page doesnt work on the main page.
If I comment out the Item template, somehow I see the list of strings bound to the UI.
if I uncomment, I see that Item template works but
If I restart the app, I need to repeat the process.
Everything with ListView Binding and collectionView Binding is screwed. We have declare the contents of lists and collections as public properties and access from ViewModel. Its hectic

The issue here is that you had set x:DataType for the page, which is awesome because it is compiled bindings, however it means you also need to set it on and DataTemplate so it knows the type of the item inside of it. So for the first ListView that is a string you would do <DataTemplate x:DataType="x:String"> and then for your customer it would be <DataTemplate x:DataType="local:Customer">
Take a look at this repo, seems to work for me based on what I see: https://github.com/jamesmontemagno/App4 & https://github.com/fewbackseven/listView/pull/1

Binding for Localization

I'm working on a solution to a localization problem. This isn't the normal language localisation.
<Label Content="{Binding myDictionary[A Test], FallbackValue=A Test}"/>
In practice the above code calls into the Dictionary in the view model, which is declared as
public Dictionary<string, string> myDictionary
The problem is that I have to define the string "A Test" twice in the label.
once as in the index in the binding, and again in the FallbackValue.
What I would like to end up with is something that looks like this...
<Label Content="{Binding myDictionary[A Test]}"/>
At the moment what happens when I do this is that the Xaml designer in Visual studio can't resolve myDictionary (as it won't know the datacontext so can't hook up to the viewmodel where it's defined) this means that the label will display as blank, which won't will make visual design harder.
I've looked into calling a static method however for myDictionary to function properly, it needs to be instantiated in the view model.
Is there a way of having either the index value "A Test" show up in the designer without having to use a fallback value?
The goal is to be able to have the content refreshed if the value in myDictionary[A Test] is updated (In reality myDictionary is observable)

as it won't know the datacontext so can't hook up to the viewmodel where it's defined
Not so.... One can use a design time only context by specifying it in the page's meta data atttributes such as:
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
d:DataContext="{d:DesignInstance {x:Type viewModels:MainVM}}"
by doing that you can setup a design time only dictionary to use.
Read about here in MSDN magazine:
MVVM - Maximizing the Visual Designer’s Usage with Design-Time Data
Note one can still use the Blend namespaces in non Blend editors such as Visual Studio. Otherwise don't be afraid to use/learn Blend as needed.
If from your actual VM with real data, in design mode its good to ignore certain objects/actions which may cause issues. Here is a check to determine if the action is in design mode, if it is not then it executes the block, otherwise it is ignored because it is in design mode.
if (!DesignerProperties.GetIsInDesignMode(this))

Best way to handle this IMO is with a custom markup extension placed within a custom namespace, it allows you to write XAML like this:
<TextBlock Text="{Translate 'Hello World!'} />
What the Translate extension class returns is entirely up to you, typically you have it do a look-up into a Dictionary using the provided string as the index and, if it doesn't find it, just returns the string itself.
One of the nice things about this particular implementation is that it adds a listener to the Translation manager for every binding that is made, so they all automatically update at run-time whenever the current language is changed.
The one thing you do have to keep in mind though is to place the Translate extension class itself within its own project. Not sure why, it seems to be a bug in VS, but XAML files don't seem to be able to use custom markup extensions declared in the same project.

Open new View when new ViewModel is available?

I am relatively new to WPF/MVVM. Our current WPF project is still a prototype application, which means we haven't come to designing of main layout. But we do have designed some reports (by reports, I mean some quite complicated UserControl each of which has some configuration controls such as ComobBoxor TextBox, and some DataGrid, Graph controls for the data we want to present) as Viewand their ViewModel. It is still prototype, so we just need to open a new Window which displays any of these UserControl. In the future, we might change it to locate different UserControl in different regions inside the main window, like the layout of Visual Studio. The MAIN point is, our application would include almost a hundred of such UserControl or what we call reports. So it is different from my previous working projects which had static layout/MainView.
I still haven't figured out a good architecture for it. Our classic usage scenario is to let the user to select in the menu report to open, and so we have Command (either in MainViewModel, or in any ViewModel of report) objects to open a new report. So basically the Command is generating a new ViewModel (ViewModel first case) and then a corresponding View should be generated (by whom?), and finally a new Window should be opened including the newly-generated UserControl.
I guess I need two services:
a service which subscribes to the new-ViewModel-generated event, and resolve the UserControl when such event happens.
(for our current prototype application) a window manager, which subscribes to the new-UserControl-generated event published by the 1) service, and then opens a new Window to display it.
And in the future for our actual application, we can change the 2) service and put them into different regions. For the second, it is simple and only temporary, I can just have one object in the code-behind of MainView, which subscribes to the event using EventAggregator, and generate a new Window. Is it correct ?
Can somebody tell me how I should achieve this?

Data binding can already handle this for you. In the container where you want to display the reports add a ContentControl and bind it to a property that holds the VM for the report that you want to display currently.
<Window>
<ContentControl Content="{Binding Path=CurrentReport}" />
</Window>
To display the different reports wrap each of the UserControls in its own DataTemplate that can be injected into the ContentControl. To actually resolve the view you have a few choices. You can create a DataTemplateSelector to map them or just specify the VM types on your templates. In either case, make sure the templates are in scope at the ContentControl (in Resources in the same file or a parent, or merged from standalone ResourceDictionary).
<DataTemplate DataType="{x:Type viewModels:FirstReportViewModel}">
<views:FirstReportViewControl/>
</DataTemplate>

John Bowen beat me to it, by I thought I'd still post, maybe it helps.
For associating views with view models you can use data templates in a resource dictionary.
<DataTemplate DataType="{x:Type vm:AllCustomersViewModel}">
<vw:AllCustomersView />
</DataTemplate>
As you probably already know, you can set namespaces within your resource dictionaries. In this example vw and vm reference the folders containing viewmodels and views respectively.
Now you can use content control to generate the views by binding to the view model.
<ContentControl Content="{Binding SomeViewModel}" />
The code above has been shamelessly stolen from Josh Smith btw.
So, you should not need a service for resolving the association of view to viewmodel. Let the framework do the work for you.
I actually do not recommend opening new windows. If you must, using a "Window Controller"-Service of some sort will be unavoidable. However, I advise you to stick to a single window containing multiple viewmodels and exchanging them upon receiving certain events.

Implement binding extension on a property

I have a control that we could identify as similar to ListBox control. Each item is represented with one element (example TextBlock). What i would like is to change the layout of this item, so that it contains two TextBlocks. So I create a ControlTemplate, put a Border Grid, TwoTextBlocks, and all is well. Now the problem:
I need to be able to localize the text in the item, and I did this normally like this:
<... Text="{Binding Strings.SomeString, Source={StaticResource ApplicationResources}}" />
Now I need to be able to do the same with both TextBlocks. So i thought I need to create a custom type that this item will bind to, and expose two propertiws: Title and Description. If I expose this properties as string type, everything works ok, but I am loosing markup binding that I used previously. How to achieve the same with two properties? The result should be like:
<... Title="{Binding Strings.SomeString, Source={StaticResource ApplicationResources}}", Description="{Binding Strings.AnotherString, Source={StaticResource ApplicationResources}}" />
I was able to make Localization work with ResourcemManager class, but it gets even complicated in order to provide localization to be applied dynamically at runtime.
So, what do I need to do to be able to use above code? Then I just need to implement INotifyPropertyChanged on ApplicationResource and all is set.

Great!
I'm going to do the same thing you did here. Yeah, I have a solution but I'm not sure if it works till now.
First, we need a LocalizationManager which holds a dictionary.
For example, if you need to localize a user account window, just do this
<TextBlock Text="something, UsernameKey">
And the localizationManager will map UsernameKey to "Username" or other language
Second, a xaml extension which find the value of the key from LocalizationManager.
I wonder if this custom extension could derived from Binding extension, if so, this'll be very easy, just create a Binding Object to the target. If not, I think holding a WEAK reference to the UIElement by xaml extension to dynamic update the text is proper.
This solution is simple but not generic. There're some language read from right to left. It asks the application to show content from right to left.
So, I have another generic solution but more complex.
Instead of xaml extension, we use an attach dependency property.
Do it like this:
<TextBlock LocalizationManager.LocalizationKey="UsernameKey" />
So, the problem now is how to set "Text" property by LocalizationManager?
We use adapters, LocalizationManager will search proper adapter for type "TextBlock"
So, when the application is booting, we register some adapters to LocalizationManager:
LocalizationManager.Current.RegisterAdapter<TextBlock>(new TextBlockAdapter())
This solution is more generic, it supports any kind of control if you provide adapter, but as you see, this solution needs more work and much more complex than the former one.
I hope these design solutions could help you~

Using XAML ItemTemplates with Metro UI

The default "split view" template for a Metro application written in C# makes use of an ItemTemplate attribute in the ListView tag. I'm just getting started with XAML and C#, so it's all still a bit overwhelming.
I understand that the ItemsSource is used to provide the data collection to the view, but I'm a bit confused as to how the ListView knows what to display from those model classes. Is this defined by the ItemTemlate? There's a snippet of code:
...ItemTemplate="{StaticResource SnapListItemTemplate}" ItemContainerStyle="{StaticResource SnapListTileStyle}" ItemsPanel="{StaticResource SnapListItemsPanelTemplate}"...
I don't really understand most of that line. Where are these SnapList* options defined? Is there a provided list of available templates, or are these all defined my project somewhere? Does the SnapListItemTemplate look for a specific set of ivars to display? Can this template be altered or "subclassed"?
For example, there are a number of properties on the model classes like title, subtitle, etc. And I'm curious as to how the ListView knows to pull out those specific values, and also how it knows to lay them out. What if I want to change the name of the subtitle ivar to subtext? How is the item template updated?

The SnapList* templates should be defined in your project somewhere.
The binding is {StaticResource ...} which means that the template/style or whatever is usually defined in some XAML file.
If you search the project (Ctrl+Shift+F) for the names they should turn up, probably in a file called Styles.xaml.