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    <p>I feel I just found a rather nice MVVM solution to this problem. I wrote a behavior that is exposing a type property <code>WindowType</code> and a boolean property <code>Open</code>. DataBinding the latter allows the ViewModel to open and close the windows easily, without knowing anything about the View.</p> <p>Gotta love behaviors... :)</p> <p><img src="https://i.stack.imgur.com/b5VVi.png" alt="enter image description here"></p> <p>Xaml:</p> <pre><code>&lt;UserControl x:Class="WpfApplication1.OpenCloseWindowDemo" 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:WpfApplication1" xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity" mc:Ignorable="d" d:DesignHeight="300" d:DesignWidth="300"&gt; &lt;UserControl.DataContext&gt; &lt;local:ViewModel /&gt; &lt;/UserControl.DataContext&gt; &lt;i:Interaction.Behaviors&gt; &lt;!-- TwoWay binding is necessary, otherwise after user closed a window directly, it cannot be opened again --&gt; &lt;local:OpenCloseWindowBehavior WindowType="local:BlackWindow" Open="{Binding BlackOpen, Mode=TwoWay}" /&gt; &lt;local:OpenCloseWindowBehavior WindowType="local:YellowWindow" Open="{Binding YellowOpen, Mode=TwoWay}" /&gt; &lt;local:OpenCloseWindowBehavior WindowType="local:PurpleWindow" Open="{Binding PurpleOpen, Mode=TwoWay}" /&gt; &lt;/i:Interaction.Behaviors&gt; &lt;UserControl.Resources&gt; &lt;Thickness x:Key="StdMargin"&gt;5&lt;/Thickness&gt; &lt;Style TargetType="Button" &gt; &lt;Setter Property="MinWidth" Value="60" /&gt; &lt;Setter Property="Margin" Value="{StaticResource StdMargin}" /&gt; &lt;/Style&gt; &lt;Style TargetType="Border" &gt; &lt;Setter Property="Margin" Value="{StaticResource StdMargin}" /&gt; &lt;/Style&gt; &lt;/UserControl.Resources&gt; &lt;Grid&gt; &lt;StackPanel&gt; &lt;StackPanel Orientation="Horizontal"&gt; &lt;Border Background="Black" Width="30" /&gt; &lt;Button Content="Open" Command="{Binding OpenBlackCommand}" CommandParameter="True" /&gt; &lt;Button Content="Close" Command="{Binding OpenBlackCommand}" CommandParameter="False" /&gt; &lt;/StackPanel&gt; &lt;StackPanel Orientation="Horizontal"&gt; &lt;Border Background="Yellow" Width="30" /&gt; &lt;Button Content="Open" Command="{Binding OpenYellowCommand}" CommandParameter="True" /&gt; &lt;Button Content="Close" Command="{Binding OpenYellowCommand}" CommandParameter="False" /&gt; &lt;/StackPanel&gt; &lt;StackPanel Orientation="Horizontal"&gt; &lt;Border Background="Purple" Width="30" /&gt; &lt;Button Content="Open" Command="{Binding OpenPurpleCommand}" CommandParameter="True" /&gt; &lt;Button Content="Close" Command="{Binding OpenPurpleCommand}" CommandParameter="False" /&gt; &lt;/StackPanel&gt; &lt;/StackPanel&gt; &lt;/Grid&gt; &lt;/UserControl&gt; </code></pre> <p>YellowWindow (Black/Purple alike):</p> <pre><code>&lt;Window x:Class="WpfApplication1.YellowWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="YellowWindow" Height="300" Width="300"&gt; &lt;Grid Background="Yellow" /&gt; &lt;/Window&gt; </code></pre> <p>ViewModel, ActionCommand:</p> <pre><code>using System; using System.ComponentModel; using System.Windows.Input; namespace WpfApplication1 { public class ViewModel : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; private void OnPropertyChanged(string propertyName) { if (this.PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } private bool _blackOpen; public bool BlackOpen { get { return _blackOpen; } set { _blackOpen = value; OnPropertyChanged("BlackOpen"); } } private bool _yellowOpen; public bool YellowOpen { get { return _yellowOpen; } set { _yellowOpen = value; OnPropertyChanged("YellowOpen"); } } private bool _purpleOpen; public bool PurpleOpen { get { return _purpleOpen; } set { _purpleOpen = value; OnPropertyChanged("PurpleOpen"); } } public ICommand OpenBlackCommand { get; private set; } public ICommand OpenYellowCommand { get; private set; } public ICommand OpenPurpleCommand { get; private set; } public ViewModel() { this.OpenBlackCommand = new ActionCommand&lt;bool&gt;(OpenBlack); this.OpenYellowCommand = new ActionCommand&lt;bool&gt;(OpenYellow); this.OpenPurpleCommand = new ActionCommand&lt;bool&gt;(OpenPurple); } private void OpenBlack(bool open) { this.BlackOpen = open; } private void OpenYellow(bool open) { this.YellowOpen = open; } private void OpenPurple(bool open) { this.PurpleOpen = open; } } public class ActionCommand&lt;T&gt; : ICommand { public event EventHandler CanExecuteChanged; private Action&lt;T&gt; _action; public ActionCommand(Action&lt;T&gt; action) { _action = action; } public bool CanExecute(object parameter) { return true; } public void Execute(object parameter) { if (_action != null) { var castParameter = (T)Convert.ChangeType(parameter, typeof(T)); _action(castParameter); } } } } </code></pre> <p>OpenCloseWindowBehavior:</p> <pre><code>using System; using System.Windows; using System.Windows.Controls; using System.Windows.Interactivity; namespace WpfApplication1 { public class OpenCloseWindowBehavior : Behavior&lt;UserControl&gt; { private Window _windowInstance; public Type WindowType { get { return (Type)GetValue(WindowTypeProperty); } set { SetValue(WindowTypeProperty, value); } } public static readonly DependencyProperty WindowTypeProperty = DependencyProperty.Register("WindowType", typeof(Type), typeof(OpenCloseWindowBehavior), new PropertyMetadata(null)); public bool Open { get { return (bool)GetValue(OpenProperty); } set { SetValue(OpenProperty, value); } } public static readonly DependencyProperty OpenProperty = DependencyProperty.Register("Open", typeof(bool), typeof(OpenCloseWindowBehavior), new PropertyMetadata(false, OnOpenChanged)); /// &lt;summary&gt; /// Opens or closes a window of type 'WindowType'. /// &lt;/summary&gt; private static void OnOpenChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { var me = (OpenCloseWindowBehavior)d; if ((bool)e.NewValue) { object instance = Activator.CreateInstance(me.WindowType); if (instance is Window) { Window window = (Window)instance; window.Closing += (s, ev) =&gt; { if (me.Open) // window closed directly by user { me._windowInstance = null; // prevents repeated Close call me.Open = false; // set to false, so next time Open is set to true, OnOpenChanged is triggered again } }; window.Show(); me._windowInstance = window; } else { // could check this already in PropertyChangedCallback of WindowType - but doesn't matter until someone actually tries to open it. throw new ArgumentException(string.Format("Type '{0}' does not derive from System.Windows.Window.", me.WindowType)); } } else { if (me._windowInstance != null) me._windowInstance.Close(); // closed by viewmodel } } } } </code></pre>
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    1. POGive some command to View in MVVM
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    1. COAh, I love behaviors...
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    2. CO+1 for behaviors
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