Binding the “WindowState” property of a window in

问题:

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?

回答1:

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).

回答2:

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");
            }
        }
    }

回答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.