WPF

public interface IViewModelLocator
{
    object Get<T>();

    void Register(Type viewType, object viewModel);
}

public class ViewModelLocator : IViewModelLocator
{
    // Internal list of View Models
    private IDictionary<Type, object> _storage;

    public ViewModelLocator()
    {
        _storage = new Dictionary<Type, object>();
    }

    public object Get<T>()
    {
        if (_storage.ContainsKey(typeof(T)))
        {
            return _storage.FirstOrDefault(x => x.Key == typeof(T)).Value;
        }
        else
        {
            throw new Exception($"The requested view '{typeof(T)}' is not registered");
        }
    }

    public void Register(Type viewType, object viewModel)
    {
        if (!_storage.ContainsKey(viewType))
        {
            _storage.Add(viewType, viewModel);
        }
        else
        {
            throw new Exception($"An instance of the view model '{viewModel}' is already registered for the view '{viewType}'");
        }
    }
}

public partial class App : Application
{
    public static IServiceLocator ServiceLocator { get; private set; }
    public static IViewModelLocator ViewModelLocator { get; private set; }

    public App()
    {
        ServiceLocator = new ServiceLocator();
        ServiceLocator.Register(typeof(IMyService), new MyService());

        ViewModelLocator = new ViewModelLocator();
        ViewModelLocator.Register(typeof(MainWindowView), new MainWindowViewModel(ServiceLocator.Get<IMyService>()));
        ViewModelLocator.Register(typeof(LoginView), new LoginViewModel());
    }
}

public partial class MainWindowView : Window
{
    public MainWindowView()
    {
        InitializeComponent();

        this.DataContext = App.ViewModelLocator.Get<MainWindowView>();
    }
}

x:Class="My.MainView"
   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
   DataContext="{Binding Source={StaticResource MyViewModelLocator}, Path=Main}">

1. It required a resources entry in App.XAML:

   <Application.Resources>
   <core:ViewModelLocator x:Key="MyViewModelLocator" />
   </Application.Resources>

2. It requires a property on the VM Locator called "Main". Since these classes are going to be in my framework, there won't be a property for each ViewModel that other apps use on the VM Locator.

DataContext="{Binding Path="{x:static TestApp:App.ViewModelLocator.Get<???????>()}"

<pre><br />
            <Grid Grid.Row="6"
                  Grid.Column="1">

                <Grid.RowDefinitions>
                    <RowDefinition Height="Auto"/>
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="Auto"/>
                    <ColumnDefinition Width="Auto"/>
                </Grid.ColumnDefinitions>

                <PasswordBox Grid.Row="0" 
                             Grid.Column="0"
                             TabIndex="2"
                             cls:PasswordBoxAssistant.BindPassword="True"
                             cls:PasswordBoxAssistant.BoundPassword="{Binding Password, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                             Visibility="Visible"
                             Width="400">

                    <PasswordBox.Style>
                        <Style TargetType="PasswordBox">
                            <Style.Triggers>
                                <DataTrigger Binding="{Binding ElementName=chkShowPassword, Path=IsChecked}" Value="False">
                                    <Setter Property="Visibility" Value="Hidden"/>
                                </DataTrigger>
                            </Style.Triggers>
                        </Style>
                    </PasswordBox.Style>

                </PasswordBox>

                <TextBox Grid.Row="0" 
                         Grid.Column="0"
                         Text="{Binding Password, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                         TabIndex="2"
                         Width="400"
                         Visibility="Hidden">

                    <TextBox.Style>
                        <Style TargetType="TextBox" BasedOn="{StaticResource textBoxStyle}">
                            <Style.Triggers>
                                <DataTrigger Binding="{Binding ElementName=chkShowPassword, Path=IsCheckd}"  Value="True">
                                    <Setter Property="Visibility" Value="Visible"/>
                                </DataTrigger>
                            </Style.Triggers>
                        </Style>
                    </TextBox.Style>

                </TextBox>

                <CheckBox Grid.Row="0" 
                          Grid.Column="1" 
                          x:Name="chkShowPassword"
                          HorizontalAlignment="Right" 
                          VerticalAlignment="Center" 
                          ToolTip="Show Password"
                          IsChecked="{Binding IsShowPasswordChecked}"
                          Style="{StaticResource showPasswordCheckBoxStyle}"/>

            </Grid>

System.NotSupportedException: Range actions are not supported.

Stack Trace: 
ListCollectionView.ValidateCollectionChangedEventArgs(NotifyCollectionChangedEventArgs e)
ListCollectionView.ProcessCollectionChanged(NotifyCollectionChangedEventArgs args)
AbstractInvocation.Proceed()
Invocation.CallBase() line 147
ReturnBaseOrDefaultValue.Execute(Invocation invocation) line 88
IInterceptor.Intercept(Invocation invocation) line 34
Interceptor.Intercept(IInvocation underlying) line 113
AbstractInvocation.Proceed()
NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)

1. When a range Add/Remove event if fired, instead fire a Reset event.
2. When a range Add/Remove event if fired, instead fire multiple Add/Remove single item events.
3. or.. mmm... have a FireEventMode property, which would let the user decide whether to use event as is, split it, or fire Reset.

<Window x:Class="Main.Views.DataGridCustomAnimation"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Main.Views"
        mc:Ignorable="d"
        Loaded="Window_Loaded"
        Title="DataGridCustomAnimation" Height="450" Width="800">

    <Window.Resources>
        <Style TargetType="{x:Type DataGridRow}" x:Key="DataGridRowSmallStyle">
            <Setter Property="Foreground" Value="Blue" />
            <Setter Property="Background" Value="LightGray" />
            <Setter Property="MinHeight" Value="26" />
            <Style.Triggers>
                <Trigger Property="IsMouseOver" Value="True">
                    <Setter Property="Background" Value="Gray" />
                </Trigger>
            </Style.Triggers>
        </Style>
    </Window.Resources>

    <Grid Margin="20">
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
            <RowDefinition Height="20" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>

        <DataGrid x:Name="grid"
                  Grid.Row="0"
                  AutoGenerateColumns="True">
            <DataGrid.Resources>
                <Style BasedOn="{StaticResource DataGridRowSmallStyle}" TargetType="{x:Type DataGridRow}">
                    <Style.Triggers>
                        <MultiDataTrigger>
                            <MultiDataTrigger.Conditions>
                                <Condition Binding="{Binding HasBirthday}" Value="True" />
                                <Condition Binding="{Binding IsMouseOver, RelativeSource={RelativeSource Self}}" Value="False" />
                                <Condition Binding="{Binding IsSelected, RelativeSource={RelativeSource Self}}" Value="False" />
                            </MultiDataTrigger.Conditions>
                            <MultiDataTrigger.EnterActions>
                                <BeginStoryboard>
                                    <Storyboard RepeatBehavior="Forever">
                                        <ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(DataGridRow.Background).(SolidColorBrush.Color)">
                                            <EasingColorKeyFrame KeyTime="0:0:0.0" Value="#ca0516"/>
                                            <EasingColorKeyFrame KeyTime="0:0:1.0" Value="#ca0516"/>
                                            <EasingColorKeyFrame KeyTime="0:0:2.0" Value="#db552c"/>
                                            <EasingColorKeyFrame KeyTime="0:0:3.0" Value="#ca0516"/>
                                        </ColorAnimationUsingKeyFrames>

                                        <!-- Note: -->
                                        <!-- Cannot set the Foreground to white with a 'setter' when using an animation. -->
                                        <ColorAnimation Storyboard.TargetProperty="(DataGridRow.Foreground).(SolidColorBrush.Color)"
                                                        From="White"
                                                        To="White" />
                                    </Storyboard>
                                </BeginStoryboard>
                            </MultiDataTrigger.EnterActions>
                        </MultiDataTrigger>
                    </Style.Triggers>
                </Style>
            </DataGrid.Resources>
        </DataGrid>

        <Button Grid.Row="2" Height="40" Width="40" Content="Test" Click="Test_Clicked" />
    </Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;

namespace Main.Views
{
    /// <summary>
    /// Interaction logic for DataGridCustomAnimation.xaml
    /// </summary>
    public partial class DataGridCustomAnimation : Window
    {
        public DataGridCustomAnimation()
        {
            InitializeComponent();
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            var list = new List<Person>();
            for (int i = 0; i < 40; i++)
            {
                list.Add(new Person
                {
                    Name = $"Person {i}"
                });
            }
            list.First().HasBirthday = true;
            grid.ItemsSource = list;
        }

        private void Test_Clicked(object sender, RoutedEventArgs e)
        {
            var hasBirthdays = (grid.ItemsSource as List<Person>).Where(x => x.HasBirthday);
            Console.WriteLine(hasBirthdays.Count());
        }
    }

    public class Person
    {
        public string Name { get; set; }
        public bool HasBirthday { get; set; }
        public bool IsDead { get; set; }
    }
}

I am trying to print labels with a height of 38mm. The number in a run can be from 1 to 2000. The preview like in a document viewer would be desirable. The label height is entered in the printer's print settings. The printer is not the default printer in the user profile. In the DocumentViewer, however, the print settings are only loaded if it is the default printer.
I want to specify the printer from a CONFIG file and the label height must be 38mm, not DIN A4!
I can't get any further without a program example. Thank you for help. 

Hey all I have the following OnStartup for my WPF desktop app that goes to a local directory and gathers all the images within that folder (box1 being the example code below):

<pre lang="C#">public partial class App : Application
    {
        protected override void OnStartup(StartupEventArgs e)
        {
            base.OnStartup(e);

            // set the update interval
            var imageSource = new ImageSource(Path.Combine(@"C:\photos\boxes\", "box1"), TimeSpan.FromHours(1));
            var viewModel = new MainWindowViewModel(imageSource);

            var window = new MainWindow()
            {
                DataContext = viewModel
            };

            window.Closed += (s, a) => { viewModel.Dispose(); };
            window.Show();
        }
    }

C:\
 |-photos\
    |boxes\
      |box1
      |box2
      |box3
      |box4
      |box5
      |box6
      |box7
      |box8
      |box9
      |box10

<Window.Resources>
        <!-- List of supported animations -->
        <FluidKit:SlideTransition x:Key="SlideTransition" x:Shared="False"/>
        <FluidKit:CubeTransition x:Key="CubeTransition" Rotation="BottomToTop" x:Shared="False"/>
        <FluidKit:FlipTransition x:Key="FlipTransition" x:Shared="False"/>
        <local:ImageSourceConverter x:Key="ImageSourceConverter"/>
        <!-- Data template for animations -->
        <DataTemplate x:Key="ItemTemplate" x:Shared="False">
            <Image Source="{Binding Path, Converter={StaticResource ImageSourceConverter}}"
                   Stretch="Fill"/>
        </DataTemplate>
    </Window.Resources>
    <Grid>
        <FluidKit:TransitionPresenter RestDuration="0:0:3"
                                          IsLooped="True"
                                        Transition="{StaticResource FlipTransition}"
                                       ItemsSource="{Binding box1}"
                                             Width="357"
                                            Height="272"
                               HorizontalAlignment="Left"
                                 VerticalAlignment="Top"
                                      ItemTemplate="{StaticResource ItemTemplate}"
                                            x:Name="box1"
                                            Margin="0,0,0,454"/>
        <FluidKit:TransitionPresenter RestDuration="0:0:3"
                                          IsLooped="True"
                                        Transition="{StaticResource FlipTransition}"
                                       ItemsSource="{Binding box2}"
                                             Width="357"
                                            Height="272"
                               HorizontalAlignment="Left"
                                 VerticalAlignment="Top"
                                      ItemTemplate="{StaticResource ItemTemplate}"
                                            x:Name="box2"
                                            Margin="357,0,0,0"/>
       ETC.......

public class MainWindowViewModel : IDisposable
{
    private readonly IDisposable _token1;
    private readonly IDisposable _token2;
    ...ETC

    public MainWindowViewModel(IImageSource imageSource)
    {
        // subscribe to update images at regular intervals
        _token1 = imageSource
            .GetImages().ObserveOn(DispatcherScheduler.Current)
            .Subscribe(i => UpdateImages(i, box1), ex => ShowError(ex));

        _token2 = imageSource
            .GetImages().ObserveOn(DispatcherScheduler.Current)
            .Subscribe(i => UpdateImages(i, box2), ex => ShowError(ex));
        ETC...
    }

    private void ShowError(Exception ex)
    {
        MessageBox.Show(ex.Message, "Photo Gallery", MessageBoxButton.OK, MessageBoxImage.Error);
    }

    /// <summary>
    /// Updates the animation's images.
    /// </summary>
    /// <param name="images">The images to update with</param>
    /// <param name="animation">The animation to update</param>
    private void UpdateImages(IEnumerable<string> images, ObservableCollection<ImageViewModel> animation)
    {
        animation.Clear();

        foreach (var i in images)
        {
            animation.Add(new ImageViewModel { Path = i });
        }
    }

    /// <summary>
    /// Gets or sets a collection of images used for the first animation.
    /// </summary>
    public ObservableCollection<ImageViewModel> box1 { get; set; } =
        new ObservableCollection<ImageViewModel>();

    public ObservableCollection<ImageViewModel> box2 { get; set; } =
        new ObservableCollection<ImageViewModel>();

    ETC...

    public void Dispose()
    {
        _token1.Dispose();
        _token2.Dispose();
        ETC...
    }
}

public class ImageSource : IImageSource
{
    private readonly string _path;
    private readonly TimeSpan _interval;

    public ImageSource(string path, TimeSpan interval)
    {
        _path = path;
        _interval = interval;
    }

    public IObservable<IEnumerable<string>> GetImages()
    {
        if (!Directory.Exists(_path))
        {
            return Observable.Empty<IEnumerable<string>>();
        }

        return Observable.Create<IEnumerable<string>>(observer =>
        {
            return TaskPoolScheduler.Default.ScheduleAsync(async (ctrl, ct) =>
            {
                for (;;)
                {
                    if (ct.IsCancellationRequested)
                    {
                        break;
                    }

                    try
                    {
                        var images = Directory.GetFiles(_path, "*.jpg");

                        // Don’t do anything unless there are a minimum of 10 images.
                        if (images.Count() > 9)
                        {
                            observer.OnNext(images.PickRandom());
                        }
                    }
                    catch (Exception ex)
                    {
                        observer.OnError(ex);
                        throw;
                    }

                    await ctrl.Sleep(_interval).ConfigureAwait(false);
                 }
            });
        });
    }