注意两个参数：

Orientation ：控制排列是水平方向，还是垂直方向（Horizontal 水平方向   Vertical垂直方向）

FlowDirection：控制控件排序是从右往左还是从左往右，写两个简单的demo如下：

<Window x:Class="StackPanel_One.MainWindow"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:d="http://schemas.microsoft.com/expression/blend/2008"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"xmlns:local="clr-namespace:StackPanel_One"mc:Ignorable="d"Title="MainWindow" Height="450" Width="800"><Grid><Grid.ColumnDefinitions><ColumnDefinition></ColumnDefinition><ColumnDefinition></ColumnDefinition><ColumnDefinition></ColumnDefinition><ColumnDefinition></ColumnDefinition></Grid.ColumnDefinitions><StackPanel Grid.Column="0" Orientation="Horizontal"><Button Width="40" Height="40"></Button><Button Width="40" Height="40"></Button></StackPanel><StackPanel Grid.Column="1" Orientation="Vertical"><Button Width="40" Height="40"></Button><Button Width="40" Height="40"></Button></StackPanel><StackPanel Grid.Column="2" Orientation="Horizontal" FlowDirection ="RightToLeft"><Button Width="40" Height="40"></Button><Button Width="40" Height="40"></Button></StackPanel><StackPanel Grid.Column="3" Orientation="Vertical" FlowDirection="RightToLeft"><Button Width="40" Height="40"></Button><Button Width="40" Height="40"></Button></StackPanel></Grid>
</Window>

效果如下：