wpf 给UserControl添加依赖属性，事件和命令

1新建wpf项目

2新建wpf UserControl库

<UserControl x:Class="CustomControl.ColorPickerUserControl"
             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:local="clr-namespace:CustomControl"
             mc:Ignorable="d" 
             d:DesignHeight="450" d:DesignWidth="800" x:Name="colorPicker">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition></ColumnDefinition>
            <ColumnDefinition Width="Auto"></ColumnDefinition>
        </Grid.ColumnDefinitions>

        <Slider Name="sliderRed" Minimum="0" Maximum="255"
             Margin="{Binding ElementName=colorPicker,Path=Padding}"
             Value="{Binding ElementName=colorPicker,Path=Red}"></Slider>

        <Slider Grid.Row="1" Name="sliderGreen" Minimum="0" Maximum="255"
             Margin="{Binding ElementName=colorPicker,Path=Padding}"
                  Value="{Binding ElementName=colorPicker,Path=Green}"></Slider>

        <Slider Grid.Row="2" Name="sliderBlue" Minimum="0" Maximum="255"
             Margin="{Binding ElementName=colorPicker,Path=Padding}"
                  Value="{Binding ElementName=colorPicker,Path=Blue}"></Slider>


        <Rectangle Grid.Column="1" Grid.RowSpan="3"
                 Margin="{Binding ElementName=colorPicker,Path=Padding}"
                 Width="50" Stroke="Black" StrokeThickness="1">
            <Rectangle.Fill>
                <SolidColorBrush Color="{Binding ElementName=colorPicker,Path=Color}"></SolidColorBrush>
            </Rectangle.Fill>
        </Rectangle>

    </Grid>
</UserControl>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace CustomControl
{
    /// <summary>
    /// ColorPickerUserControl.xaml 的交互逻辑
    /// </summary>
    public partial class ColorPickerUserControl : UserControl
    {
        public ColorPickerUserControl()
        {
            InitializeComponent();
        }

        public Color Color
        {
            get { return (Color)GetValue(ColorProperty); }
            set { SetValue(ColorProperty, value); }
        }

        public byte Red
        {
            get { return (byte)GetValue(RedProperty); }
            set { SetValue(RedProperty, value); }
        }
        public byte Green
        {
            get { return (byte)GetValue(GreenProperty); }
            set { SetValue(GreenProperty, value); }
        }

        public byte Blue
        {
            get { return (byte)GetValue(BlueProperty); }
            set { SetValue(BlueProperty, value); }
        }

        public static readonly DependencyProperty ColorProperty =
            DependencyProperty.Register("Color", typeof(Color), typeof(ColorPickerUserControl), new PropertyMetadata(Colors.Black,OnColorChanged));

        public static readonly DependencyProperty RedProperty =
            DependencyProperty.Register("Red", typeof(byte), typeof(ColorPickerUserControl), new PropertyMetadata(OnColorRGBChanged));

        public static readonly DependencyProperty GreenProperty =
            DependencyProperty.Register("Green", typeof(byte), typeof(ColorPickerUserControl), new PropertyMetadata(OnColorRGBChanged));

        public static readonly DependencyProperty BlueProperty =
            DependencyProperty.Register("Blue", typeof(byte), typeof(ColorPickerUserControl), new PropertyMetadata(OnColorRGBChanged));

        private static void OnColorRGBChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            ColorPickerUserControl uc = (ColorPickerUserControl)d;
            Color color = uc.Color;
            if (e.Property==RedProperty)
            {
                color.R = (byte)e.NewValue;
            }
            else if (e.Property==GreenProperty)
            {
                color.G = (byte)e.NewValue;
            }
            else if (e.Property == BlueProperty)
            {
                color.B = (byte)e.NewValue;
            }
            uc.Color = color;
        }

        private static void OnColorChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            ColorPickerUserControl uc = (ColorPickerUserControl)d;
            Color color = (Color)e.NewValue;
            uc.Red = color.R;
            uc.Green = color.G;
            uc.Blue = color.B;

            Color oldColor = (Color)e.OldValue;
            uc.PreviousColor = oldColor;

            RoutedPropertyChangedEventArgs<Color> args = new RoutedPropertyChangedEventArgs<Color>(oldColor, color);
            args.RoutedEvent = ColorChangedEvent;
            uc.RaiseEvent(args);

        }


        public static readonly RoutedEvent ColorChangedEvent = EventManager.RegisterRoutedEvent("ColorChanged", RoutingStrategy.Bubble,
            typeof(RoutedPropertyChangedEventHandler<Color>), typeof(ColorPickerUserControl));

        public event RoutedPropertyChangedEventHandler<Color> ColorChanged
        {
            add { AddHandler(ColorChangedEvent, value); }
            remove { RemoveHandler(ColorChangedEvent, value); }
        }


        Color? PreviousColor;
        static ColorPickerUserControl()
        {
            CommandManager.RegisterClassCommandBinding(typeof(ColorPickerUserControl), 
                new CommandBinding(ApplicationCommands.Undo,Undo_Executed, Undo_CanExecute));
        }

        private static void Undo_CanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            ColorPickerUserControl uc = (ColorPickerUserControl)sender;
            e.CanExecute = uc.PreviousColor.HasValue;
        }

        private static void Undo_Executed(object sender, ExecutedRoutedEventArgs e)
        {
            ColorPickerUserControl uc = (ColorPickerUserControl)sender;
            uc.Color = (Color)uc.PreviousColor;
        }
    }
}

 3 主程序

<Window x:Class="CustomControlApp.ColorPickerUserControlTest"
        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:CustomControlApp"
        xmlns:lib="clr-namespace:CustomControl;assembly=CustomControl"
        mc:Ignorable="d"
        Title="ColorPickerUserControlTest" Height="450" Width="800">
    <StackPanel>
       
        <lib:ColorPickerUserControl Name="ColorPicker" ColorChanged="ColorPickerUserControl_ColorChanged"/>
        <TextBlock x:Name="lblColor"/>
        <Button Content="Undo" Command="Undo" CommandTarget="{Binding ElementName=ColorPicker}" />
    </StackPanel>
</Window>

using CustomControl;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;

namespace CustomControlApp
{
    /// <summary>
    /// ColorPickerUserControlTest.xaml 的交互逻辑
    /// </summary>
    public partial class ColorPickerUserControlTest : Window
    {
        public ColorPickerUserControlTest()
        {
            InitializeComponent();
        }

        private void ColorPickerUserControl_ColorChanged(object sender, RoutedPropertyChangedEventArgs<Color> e)
        {
            ColorPickerUserControl uc = (ColorPickerUserControl)sender;
            lblColor.Text = $"Current color is {uc.Color}";
        }
    }
}