WPF 棱镜 MVVM 从网格控件中获取所选项

我有一个DevExpress Grid Control。我想根据网格控件中的选定行启用/禁用按钮，即，如果在网格控件中选择了任何行，则应启用此按钮。以下是我的网格控制代码：

<dxg:GridControl x:Name="gridFloorplans" Grid.Column="1" Grid.Row="1" AutoGenerateColumns="None" 
            ItemsSource="{Binding FloorplanList.Result.View}"
            SelectedItems="{Binding SelectedFloorplan,Mode=TwoWay}"
            dx:ThemeManager.Theme="Default" SelectionMode="Row">
        <dxg:GridControl.View>
            <dxg:TableView AllowGrouping="False" ShowGroupPanel="False" AllowEditing="False"  ShowDataNavigator="True" DataNavigatorButtons="Navigation" />
        </dxg:GridControl.View>
        <dxg:GridControl.Columns>
            <dxg:GridColumn FieldName="Name" Header="Floorplan Name" Fixed="Left" />
            <dxg:GridColumn FieldName="Season"  Fixed="Left" />
            <dxg:GridColumn FieldName="Version"  Fixed="Left" />                
        </dxg:GridControl.Columns>            
</dxg:GridControl>

以下是我的视图模型代码：

private ObservableCollection<FloorplanData> _selectedFloorplan;
public FloorplanSearchViewModel(IErrorHandlerService inErrorHandler, INavigationService inNavigationService, 
            ISpaDataAdapter inDataAdapter, IAuthorizationService inAuthService)
{            
    // Set the commands
    this.ShowStoreSetCommand = new DelegateCommand<IList<object>>(this.ShowStoreSet, this.CanShowStoreSet);
    this.SearchFloorplansCommand = new DelegateCommand(this.SearchFloorplans);
    this.ShowStatusChangeCommand = new DelegateCommand<IList<object>>(this.ShowStatusChange, this.CanShowStatusChange);
    // Set up the default values for the search
    this.StatusList = new List<object>();
    this.StatusList.Add(Enum.GetName(typeof(FloorplanData.FloorplanStatus), FloorplanData.FloorplanStatus.Pending));
    this.StatusList.Add(Enum.GetName(typeof(FloorplanData.FloorplanStatus), FloorplanData.FloorplanStatus.Review));
    //Initiate the SelectedFloorplan property
    //SelectedFloorplan = new ObservableCollection<FloorplanData>();
}

public ObservableCollection<FloorplanData> SelectedFloorplan
{
    get
    {
        return _selectedFloorplan;
    }
    set
    {
        _selectedFloorplan = value;
        this.ShowStatusChangeCommand.RaiseCanExecuteChanged();
    }
}
public NotifyTaskCompletion<CollectionViewSource> FloorplanList
{
    get;
    private set;
}
private void ShowStatusChange(IList<object> inFloorplans)
{
    try
    {
        // Create the navigation output
        NavigationParameters args = new NavigationParameters();
        args.Add(FloorplanStatusChangeViewModel.PARAM_FLOORPLAN_ID_LIST, GetFloorplanIdList(inFloorplans));
        _navigationService.NavigateTo<Views.FloorplanStatusChangeView>(args);
    }
    catch (Exception ex)
    {
        _errorHandler.HandleError(ex);
    }
}
private bool CanShowStatusChange(IList<object> inFloorplans)
{
    // Check security to see if the current user is allowed to enter the status change screen
    if (_authService.GetAccessLevel(1470) > AuthorizationLevel.None)
    {
        if (SelectedFloorplan!=null)
            return true;
        else
            return false;
    }
    else
    {
        return false;
    }
}

下面是按钮的 xaml 代码：

<Button Margin="4,2" Content="Status Change"  Command="{Binding ShowStatusChangeCommand}" 
                    CommandParameter="{Binding SelectedItems, ElementName=gridFloorplans}">
                <Button.Style>
                    <Style TargetType="Button">
                        <Setter Property="ToolTip" Value="Open the Floorplan Status Change view for the selected floorplans" />
                        <Style.Triggers>
                            <Trigger Property="IsEnabled" Value="False">
                                <Setter Property="ToolTip" Value="You do not have access to open the Floorplan Status Change view" />
                            </Trigger>
                            <DataTrigger 
                                Binding ="{Binding ElementName=gridFloorplans, Path=SelectedFloorplan}" 
                                Value="-1">
                                <Setter Property="Button.IsEnabled" Value="false"/>
                            </DataTrigger>
                        </Style.Triggers>
                    </Style>
                </Button.Style>
            </Button>

如何根据是否在网格中选择任何行来启用/禁用"显示状态"按钮？