怎的仅通过xaml实现页面淡入淡出切换

怎样仅通过xaml实现页面淡入淡出切换
wpf中实现点击几个按钮，主窗口区域淡入淡出切换页面，我用的方法需要在cs里面写代码，想研究一下怎么在xaml里面就实现，最好同时按钮的click相应在cs里面还能响应，处理一些后台的东西？
------解决方案--------------------
不知是不是这样

<Window x:Class="WpfApplication1.Window1"

        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

        Title="Window1" Height="300" Width="300">


    <Window.Triggers>

        <EventTrigger RoutedEvent="Loaded">

            <BeginStoryboard>

                <Storyboard >

                    <DoubleAnimation Duration="0:0:3" Storyboard.TargetProperty="Opacity" From="0" To="1" />

                </Storyboard>

            </BeginStoryboard>

        </EventTrigger>

    </Window.Triggers>


    <Grid Background="Khaki"/>

</Window>