WPF MVVM Multibinding - 如何使用 RelayCommand 将两个参数传递给 Command

Question

如何使用 RelayCommand 将 2 个参数传递给命令。我需要将控件作为参数传递（网格和 Window）。我完全知道 Stack Overflow 上已经存在此类问题，但我正在努力根据自己的需要进行调整。

看看我的第一次尝试如下。它显然不起作用，因为中继无法获得 2 个参数。

Xaml代码：

        <Button Name="StretchScreenBtn" Content="Stretch screen" DataContext="   {StaticResource CommandWindow}" Command="{Binding ResizeScreenCommand}"
                Width="100" Height="50">
             <Button.CommandParameter>
                <MultiBinding Converter="{StaticResource CommandParamsConv}">
                    <Binding ElementName="ScreenGrid" />
                    <Binding RelativeSource="{RelativeSource AncestorType=Window}" /> 
                </MultiBinding> 
            </Button.CommandParameter>  
        </Button>

来自 ViewModel 的命令代码：

        private ICommand _ResizeScreenCommand;
        public ICommand ResizeScreenCommand
        {
            get
            {
                if (_ResizeScreenCommand == null)
                {
                    _ResizeScreenCommand = new RelayCommand(
                        (argument1, argument2) =>
                        {

                            Grid grid = argument1 as Grid;
                            Window window = argument2 as Window;
                            if ((int)grid.GetValue(Grid.ColumnSpanProperty) == 2)
                            {
                                grid.SetValue(Grid.ColumnSpanProperty, 1);
                                window.WindowStyle = WindowStyle.None;
                            }
                            else
                            {
                                grid.SetValue(Grid.ColumnSpanProperty, 2);
                                window.WindowStyle = WindowStyle.SingleBorderWindow;
                            }
                        }
                        );
                }
                return _ResizeScreenCommand;
            }
        }

和多值转换器：

     class CommandParamsConverter : IMultiValueConverter
     {
        public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            object[] parameters = values;
            return parameters;
        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
        {
            throw new NotImplementedException();
        }
     }

我的第二次尝试是按照 How to Passing multiple parameters RelayCommand?

因此，我在 ViewModel 中创建了新的 class，具有两个属性 Grid 和 Window 类型，然后尝试将 xaml 元素绑定到这些属性。但在这种情况下，编译器会抱怨这些属性是非依赖性的，无法绑定。

请给我任何解决方法的提示？

下面是修改后的xaml代码：

        <Button Name="StretchScreenBtn" Content="Stretch screen" DataContext="{StaticResource CommandWindow}" Command="{Binding ResizeScreenCommand}"
                Width="100" Height="50">
             <Button.CommandParameter>
                <vm:StretchingModel Grid="{Binding ElementName=ScreenGrid}" Win="{Binding RelativeSource={RelativeSource AncestorType=Window}}" />
            </Button.CommandParameter>  
        </Button>

ViewModel 中的附加 class：

    class StretchingModel
    {
        public Grid Grid { get; set; }
        public Window Win { get; set; }
    }

Answer 1

将 Grid 和 Window 传递给视图模型不是 MVVM...视图模型不应依赖任何 UI 元素。

无论如何，要将多个值传递给命令，您应该结合使用两种方法。转换器应该 return 一个 StretchingModel:

的实例

class CommandParamsConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return new StretchingModel() { Grid = values[0], Window = values[1] };
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

...命令接受：

private ICommand _ResizeScreenCommand;
public ICommand ResizeScreenCommand
{
    get
    {
        if (_ResizeScreenCommand == null)
        {
            _ResizeScreenCommand = new RelayCommand(
                (argument) =>
                {

                    StretchingModel model = argument as StretchingModel;
                    ...
                }
                );
        }
        return _ResizeScreenCommand;
    }
}

WPF MVVM Multibinding - 如何使用 RelayCommand 将两个参数传递给 Command

WPF MVVM Multibinding - How to pass two parameters to Command using RelayCommand

wpf

command

mvvm

relaycommand

multibinding