xaml页面和viewmodel之间接收绑定的参数，也可以称为事件里动态传入用户自定义参数

//xaml代码，高亮部分就是向绑定层动态传入参数
<controls:UserControl1
    x:Name="pg"
    Grid.Row="3"
    Margin="0,10,0,10"
    HorizontalAlignment="Center"
    IsResultDisplay="True"
    PageSize="{Binding PageSize, Mode=TwoWay}"
    TotalCount="{Binding TotalCount, Mode=TwoWay}"
    Visibility="Visible"
    PageIndex="{Binding PageIndex, Mode=TwoWay, NotifyOnTargetUpdated=True}">
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="PagerIndexChanged">
            <i:InvokeCommandAction Command="{Binding PagerIndexChangedCommand}" CommandParameter="{Binding ElementName=pg, Path=PageIndex, Mode=TwoWay}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
</controls:UserControl1>
        

//viewmodel代码，int? p就是页面传入的参数
public ICommand PagerIndexChangedCommand { get { return new DelegateCommand<int?>(p => PagerIndexChanged(p)); } }

void PagerIndexChanged(int? index)
{

}