c# - MVVMLight：RelayCommand 似乎在 Windows 8 应用程序中不起作用

Question

我有以下视图模型：

public class TransportationUnit : ViewModelBase {
    private string _TypeOfFuel;
    private string _Model;
    private string _Manufacturer;
    private string _LicencePlate;
    private Guid _Key = Guid.Empty;

    public ICommand CmdAddTransportationUnit { get; set; }

    public TransportationUnit() {
        CmdAddTransportationUnit = new GalaSoft.MvvmLight.Command.RelayCommand( () => AddTransportationUnitDo(), () => AddTransportationUnitCan() );
    }

    /// <summary>manufacturer</summary>
    public string Manufacturer {
          get { return _Manufacturer; }
          set {
            if (_Manufacturer == value )
                return;
            RaisePropertyChanging( "Manufacturer" );
            _Manufacturer = value;
            RaisePropertyChanged( "Manufacturer" );
        }
    }

    /* ommitted some equal properties */

    public bool AddTransportationUnitCan() {
        return !string.IsNullOrWhiteSpace( Model ) && !string.IsNullOrWhiteSpace( Manufacturer ) & !string.IsNullOrWhiteSpace( LicencePlate );
    }

    public async void AddTransportationUnitDo() {
        await LogbookRepository.Instance.Add<TransportationUnit>( this );
    }
}

我的文本框是这样绑定的：

<TextBox x:Name="CarManufacturerNameText" Width="400" HorizontalAlignment="Left" VerticalAlignment="Center" Grid.Row="0" Grid.Column="1" Text="{Binding Manufacturer,Mode=TwoWay}" />

我在 AppBar（底部）中的按钮是这样绑定的：

<Button Style="{StaticResource SaveAppBarButtonStyle}" AutomationProperties.Name="" x:Name="save" x:Uid="StandardSave" Command="{Binding CmdAddTransportationUnit}" />

我本来希望当方法AddTransportationUnitCan评估为 false 时按钮被禁用，反之亦然。当所有文本框都填满时，它会一直被禁用，甚至在方法中设置的断点也只会在创建 RelayCommand 时触发一次。我已经测试了很长时间，但没有找到解决方案。还有其他人有这个问题吗？

编辑：当我在按钮中返回 true 时AddTransportationUnitCan启用

Answer 1

尝试将 RaiseCanExecuteChanged 添加到您的属性设置器。这将告诉您的 RelayCommand 重新评估 CanExecute。

public string Manufacturer {
          get { return _Manufacturer; }
          set {
            _Manufacturer = value;
            RaisePropertyChanged( "Manufacturer" );
            CmdAddTransportationUnit.RaiseCanExecuteChanged(); 
        }
    }