Binding the "WindowState" property of a window in WPF using MVVM - wpf

Question

I bound the "WindowState" property of my main window to my ViewModel in order to change the state of the window by a command, but the first time I minimize the window it minimizes like a worksheet does in an Excel file. Is there a work around for this or a correct way to bind the "WindowState" property to my ViewModel so that the window minimizes correctly?

Answer 1

this is a sample work around that tested with Relaying Command Logic. You will get more detail on WPF Apps With The Model-View-ViewModel Design Pattern .
<Window x:Class="WpfMvvmTestCSharp.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vm="clr-namespace:WpfMvvmTestCSharp"
Title="Window1" Height="300" Width="300" WindowState="{Binding CurWindowState, Mode=TwoWay}">
<Window.DataContext>
<vm:Window1ViewModel/>
</Window.DataContext>
<Grid>
<Button Command="{Binding CmdMax}" Height="23" Margin="12,25,0,0" Name="button1" VerticalAlignment="Top" HorizontalAlignment="Left" Width="75">Maximize</Button>
<Button Command="{Binding CmdMin}" Height="23" Margin="101,25,102,0" Name="button2" VerticalAlignment="Top">Minimize</Button>
<Button Command="{Binding CmdRes}" Height="23" HorizontalAlignment="Right" Margin="0,25,13,0" Name="button3" VerticalAlignment="Top" Width="75">Restore</Button>
</Grid>
</Window>
and in the Windows ViewModel
class Window1ViewModel:ViewModelBase
{
public Window1ViewModel()
{
CurWindowState = WindowState.Maximized;
}
public ICommand CmdMax
{
get { return new RelayCommand(param => onCmdMax()); }
}
void onCmdMax()
{
CurWindowState = WindowState.Maximized;
}
public ICommand CmdMin
{
get { return new RelayCommand(param => onCmdMin()); }
}
void onCmdMin()
{
CurWindowState = WindowState.Minimized;
}
public ICommand CmdRes
{
get { return new RelayCommand(param => onCmdRes()); }
}
void onCmdRes()
{
CurWindowState = WindowState.Normal;
}
private WindowState _curWindowState;
public WindowState CurWindowState
{
get
{
return _curWindowState;
}
set
{
_curWindowState = value;
base.OnPropertyChanged("CurWindowState");
}
}
}

Answer 2

I don't think you should care about the window state in a view model, it's completely wrong because a lower-level layer is aware of a higher-level layer (thus wrong Separation of Concerns (SOC)).
What I normally do in this case is subscribe to changes in the view model from the code-behind of the control or window (thus the view) containing the view model. In this case, it is valid to write code in the code-behind because it is only used in the view (and thus the code-behind is the perfect location for this logic, which you really don't want to unit test).

Answer 3

Another option to consider is subscribing both via a command AND an event to code behind, e.g:
<Button Command="{Binding SnoozeCommand}" Click="Button_Click">Snooze</Button>
The command in this case affects the VM. The Click event, only changes the Window state.

Answer 4

I have found my own solution which is perfectly suited to MVVM. I'm using behavior to find the parent window of the user control and track WindowState changes.
public class WindowStateBehavior : Behavior<UserControl>
{
public static readonly DependencyProperty WindowStateProperty =
DependencyProperty.Register(nameof(WindowState), typeof(WindowState), typeof(WindowStateBehavior),
new FrameworkPropertyMetadata(default(WindowState), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
private Window window;
public WindowState WindowState
{
get => (WindowState) GetValue(WindowStateProperty);
set => SetCurrentValue(WindowStateProperty, value);
}
protected override void OnAttached()
{
base.OnAttached();
this.window = Window.GetWindow(this.AssociatedObject)!;
this.window.StateChanged += this.OnStateChanged;
}
private void OnStateChanged(object sender, EventArgs e) => this.WindowState = this.window.WindowState;
}
This behavior can be used in any UserControl like this with bound WindowState in ViewModel.
<UserControl x:Class="RCBase.WPF.Monitor.CustomUserView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
xmlns:behaviors="clr-namespace:RCBase.WPF.Behaviors"
mc:Ignorable="d" d:DataContext="{d:DesignInstance monitor:CustomUserViewModel}">
<i:Interaction.Behaviors>
<behaviors:WindowStateBehavior WindowState="{Binding WindowState}" />
</i:Interaction.Behaviors>