简介
"用户控件"继承自UserControl,而UserControl继承自ContentControl,也就是内容控件UserControl和Window是一个层次上的，都有xaml和cs文件
流程
创建用户控件
写好用户控件
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" mc:Ignorable="d" d:DesignHeight="300" d:DesignWidth="300">
用户控件也可以套用用户控件，组成更复杂的界面
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:userControlDemo="clr-namespace:WpfDemo.UserControlDemo" mc:Ignorable="d" d:DesignHeight="300" d:DesignWidth="300">
窗体引用用户控件
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:userControlDemo="clr-namespace:WpfDemo.UserControlDemo" mc:Ignorable="d" Title="UseUserControlWindow" Height="600" Width="400">
示例代码
https://github.com/zLulus/NotePractice/tree/dev3/WPF/WpfDemo/UserControlDemo