WPF UserControl绑定的一个需要注意的地方

注意绑定的模式尽量设为Mode=TwoWay ,UpdateSourceTrigger=PropertyChanged,这样才能激发ViewModel里面的PropertyChanged事件

UserControl代码

<UserControl
    x:Class="UserControl绑定.TitleTextBox"
    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:local="clr-namespace:UserControl绑定"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    d:DesignHeight="450"
    d:DesignWidth="800"
    mc:Ignorable="d">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="3*" />
            <ColumnDefinition Width="7*" />
        </Grid.ColumnDefinitions>
        <TextBlock Grid.Column="0" Text="{Binding Path=Title, RelativeSource={RelativeSource AncestorType=local:TitleTextBox, Mode=FindAncestor}}" />
        <TextBox Grid.Column="1" Text="{Binding Path=Text, RelativeSource={RelativeSource AncestorType=local:TitleTextBox, Mode=FindAncestor}}" />
    </Grid>
</UserControl>

后台

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 UserControl绑定
{
    /// <summary>
    /// TitleTextBox.xaml 的交互逻辑
    /// </summary>
    public partial class TitleTextBox : UserControl
    {
        // Using a DependencyProperty as the backing store for Title.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty TitleProperty =
            DependencyProperty.Register("Title", typeof(string), typeof(TitleTextBox), new PropertyMetadata(default));

        // Using a DependencyProperty as the backing store for Text.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty TextProperty =
            DependencyProperty.Register("Text", typeof(string), typeof(TitleTextBox), new PropertyMetadata(default));

        public string Title
        {
            get { return (string)GetValue(TitleProperty); }
            set { SetValue(TitleProperty, value); }
        }

        public string Text
        {
            get { return (string)GetValue(TextProperty); }
            set { SetValue(TextProperty, value); }
        }

        public TitleTextBox()
        {
            InitializeComponent();
        }
    }
}

Vm代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;

namespace UserControl绑定
{
    public class MainViewModel : INotifyPropertyChanged
    {
        private string _name;

        private string _nickName;

        private string _displayInfo;

        public string Name
        {
            get => _name;

            set
            {
                _nickName = value;
                Raise(nameof(Name));
            }
        }

        public string NickName
        {
            get => _nickName;

            set
            {
                _nickName = value;
                Raise(nameof(NickName));
            }
        }

        public string DisplayInfo
        {
            get => _displayInfo;

            set
            {
                _displayInfo = value;
                Raise(nameof(DisplayInfo));
            }
        }

        public MainViewModel()
        {
            PropertyChanged += (s, e) =>
            {
                MessageBox.Show("属性被更改！");
            };
        }

        public event PropertyChangedEventHandler PropertyChanged;

        public void Raise(string name)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
        }
    }
}

界面代码

<Window
    x:Class="UserControl绑定.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:local="clr-namespace:UserControl绑定"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Title="MainWindow"
    Width="800"
    Height="450"
    mc:Ignorable="d">
    <Window.DataContext>
        <local:MainViewModel />
    </Window.DataContext>
    <Grid>
        <StackPanel
            HorizontalAlignment="Center"
            VerticalAlignment="Center"
            Orientation="Vertical">
            <local:TitleTextBox
                Title="Name:"
                MinWidth="240"
                Text="{Binding Name, UpdateSourceTrigger=LostFocus}" />
            <local:TitleTextBox
                Title="NickName:"
                MinWidth="240"
                Margin="0,5"
                Text="{Binding NickName, UpdateSourceTrigger=LostFocus}" />
            <local:TitleTextBox
                Title="DisplayInfo:"
                MinWidth="240"
                Text="{Binding DisplayInfo, UpdateSourceTrigger=LostFocus}" />
        </StackPanel>
    </Grid>
</Window>

 

测试一下

 

 

可以看到，并没有激活VM中的事件

把Mode改变一下

 

再次测试

这次能够触发事件了