使用IMultiValueConverter将多个CommandParameter传递给viewModel

Question

我有以下代码:

<DataGridTemplateColumn Header="Security">
                        <DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                                <Button Name="Security" Content="{Binding Path=totalSecurities}" Command="{Binding Source={StaticResource viewModel}, Path=filterGridCommand}">
                                    <Button.CommandParameter>
                                        <MultiBinding Converter="{StaticResource PassThroughConverter}">
                                            <Binding Path="sector"/>
                                            <Binding ElementName="Security" Path="Name"/>
                                        </MultiBinding>
                                    </Button.CommandParameter>

                                </Button>
                            </DataTemplate>
                        </DataGridTemplateColumn.CellTemplate>
                    </DataGridTemplateColumn>

以下是PassThroughConverter的代码:

public class PassThroughConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameters, CultureInfo culture)
    {

        return values;
    }

    public object[] ConvertBack(object value, Type[] targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

当我在命中返回值行时调试,正确的值在数组中,但是当我按下触发filtergrid命令的按钮时,返回的值都是null？谁能帮忙.谢谢.

Answer 1

一些实验证实了这样做

public object Convert(object[] values, Type targetType, 
                      object parameters, CultureInfo culture)
{
    return values;
}

导致命令参数结束为object[] { null, null }.

每次绑定值更改时都会运行转换器,而不是在执行命令时运行,并且在执行命令时缓存返回值以供使用.原始参数object[] values似乎重置为所有空值.

解决方案是克隆values参数.在你的情况下,你可以这样做:

public object Convert(object[] values, Type targetType, 
                      object parameter, CultureInfo culture)
{
    return new [] {values[0], values[1]};
}

更有用的是,可以像这样处理可变数量的值:

public object Convert(object[] values, Type targetType, 
                      object parameter, CultureInfo culture)
{
    return values.ToArray();
}