public static readonly DependencyProperty IsSpinningProperty = DependencyProperty.Register(
"IsSpinning",
typeof(bool),
typeof(MainWindow)
);
public bool IsSpinning
{
get => (bool)GetValue(IsSpinningProperty);
set => SetValue(IsSpinningProperty, value);
}
2.定义 - 中译中后
在看定义之前，先来看两段代码，一个是C#中普通属性的示例代码，一个是WPF的依赖属性的示例代码
c#复制代码
// C# -> 普通属性(CLR普通属性)
public string Name
{
set => name = value;
get => name;
}
/* ================================================================================= */
// WPF -> 依赖属性
// 输入propdp，然后连续按两下Tab键，VS会帮我们自动生成下面的这段代码
public int MyProperty
{
get { return (int)GetValue(MyPropertyProperty); }
set { SetValue(MyPropertyProperty, value); }
}
// Using a DependencyProperty as the backing store for MyProperty.
// This enables animation, styling, binding, etc...
public static readonly DependencyProperty MyPropertyProperty =
DependencyProperty.Register(
"MyProperty",
typeof(int),
typeof(ownerclass),
new PropertyMetadata(0));
然后，初见依赖属性的这段代码，大多数人都是看不懂的，我们来逐行解释一下
c#复制代码
// MyProperty成员，使用CLR属性包装器实现get和set => 参考普通属性
public int MyProperty
{
// 并且使用了GetValue 和 SetValue成员 读/写 依赖属性 MyPropertyProperty
// GetValue和SetValue -> 由DependencyObject类定义的
// GetValue -> 获取依赖属性值
// SetValue -> 写入依赖属性值
get { return (int)GetValue(MyPropertyProperty); }
set { SetValue(MyPropertyProperty, value); }
}
// Using a DependencyProperty as the backing store for MyProperty.
// This enables animation, styling, binding, etc...
// 翻译一下官方的这两句话：
// 使用依赖属性作为 MyProperty 的存储方式
// 再翻译一下：MyProperty 的真实存储位置是一个 DependencyProperty，而不是字段
// 从而启用动画、样式、数据绑定等功能
/* 注册int类型的依赖属性 MyProperty */
// 被声明为 DependencyProperty 类型的静态只读类型的 MyPropertyProperty 成员
// 使用 DependencyProperty 的Register方法注册
public static readonly DependencyProperty MyPropertyProperty =
DependencyProperty.Register(
"MyProperty", // 属性名，必须与上面的包装属性名称一致
typeof(int), // 属性类型
typeof(ownerclass), // 属性所属类型 -> 这个属性"属于谁"
new PropertyMetadata(0)); // 默认值 -> 可以不写
但是上面只是一个依赖属性的模板，下面是一个实际的代码案例
c#复制代码
// 依赖属性(读取和写入) -> 具备自动通知界面的能力
public string MyPasswordVM
{
get { return (string)GetValue(MyPasswordVMProperty); }
set { SetValue(MyPasswordVMProperty, value); }
}
// 注册string类型的依赖属性 MyPasswordVM
public static readonly DependencyProperty MyPasswordVMProperty =
DependencyProperty.Register(
"MyPasswordVM", // 属性名，必须与上面的包装属性名称一致
typeof(string), // 属性类型
typeof(MainWindow)); // 所属类型
/* MyControl.cs */
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
namespace Test
{
public class MyControl : Control
{
static MyControl()
{
// 指定默认样式，如果有自定义样式可以用这个
DefaultStyleKeyProperty.OverrideMetadata(
typeof(MyControl),
new FrameworkPropertyMetadata(typeof(MyControl)));
}
public static readonly DependencyProperty MyTitleProperty =
DependencyProperty.Register(
"MyTitle", // 属性名
typeof(string), // 属性类型
typeof(MyControl), // 所属类
new PropertyMetadata( // 元数据
"默认标题", // 默认值
new PropertyChangedCallback(OnMyTitleChanged)) // 改变回调
);
public string MyTitle
{
get => (string)GetValue(MyTitleProperty);
set => SetValue(MyTitleProperty, value);
}
// 改变回调
private static void OnMyTitleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var control = d as MyControl;
// 当属性变化时打印新值
System.Diagnostics.Debug.WriteLine($"MyTitle 改变为：{e.NewValue}");
// 更新主窗口标题
if (control != null)
{
// 找到依赖属性所在的窗口
var window = Window.GetWindow(control);
if (window != null)
{
window.Title = e.NewValue?.ToString(); // 更新主窗口标题
}
}
}
}
}
c#复制代码
/* MainWindow.xaml.cs */
using System;
using System.Windows;
namespace Test
{
/// <summary>
/// MainWindow.xaml 的交互逻辑
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
// myControl 是 MainWindow.xaml 中定义的控件实例
// 对应创建的自定义控件 MyControl
myControl.MyTitle = "我是窗口";
}
private void Button_Click(object sender, RoutedEventArgs e)
{
// 点击按钮时更新依赖属性
myControl.MyTitle = textBox.Text;
}
}
}
// WPF -> 依赖属性
// 输入propdp，然后连续按两下Tab键，VS会帮我们自动生成下面的这段代码
public int MyProperty
{
get { return (int)GetValue(MyPropertyProperty); }
set { SetValue(MyPropertyProperty, value); }
}
// Using a DependencyProperty as the backing store for MyProperty.
// This enables animation, styling, binding, etc...
public static readonly DependencyProperty MyPropertyProperty =
DependencyProperty.Register(
"MyProperty",
typeof(int),
typeof(ownerclass),
new PropertyMetadata(0));
// WPF -> 附加属性
// 输入propa，然后连续按两下Tab键，VS会帮我们自动生成下面的这段代码
public static int GetMyProperty(DependencyObject obj)
{
return (int)obj.GetValue(MyPropertyProperty);
}
public static void SetMyProperty(DependencyObject obj, int value)
{
obj.SetValue(MyPropertyProperty, value);
}
// Using a DependencyProperty as the backing store for MyProperty.
//This enables animation, styling, binding, etc...
public static readonly DependencyProperty MyPropertyProperty =
DependencyProperty.RegisterAttached(
"MyProperty",
typeof(int),
typeof(ownerclass),
new PropertyMetadata(0));
using System.Windows;
using MVVM.ViewModel;
using MVVM.Helpers;
namespace MVVM.Views
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = new VMod();
}
private void Button_Click(object sender, RoutedEventArgs e)
{
var vm = (VMod)DataContext;
MessageBox.Show(vm.Password);
}
}
}
c#复制代码
/* PasswordHelper.cs */
using System.Windows;
using System.Windows.Controls;
namespace MVVM.Helpers
{
public static class PasswordHelper
{
public static readonly DependencyProperty PasswordProperty =
DependencyProperty.RegisterAttached(
"Password",
typeof(string),
typeof(PasswordHelper),
new FrameworkPropertyMetadata(
string.Empty,
//null,
FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
OnPasswordChanged));
public static void SetPassword(DependencyObject obj, string value)
{
obj.SetValue(PasswordProperty, value);
}
public static string GetPassword(DependencyObject obj)
{
return (string)obj.GetValue(PasswordProperty);
}
private static void OnPasswordChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if (d is not PasswordBox box)
return;
box.PasswordChanged -= PasswordBox_PasswordChanged;
if (box.Password != (string)e.NewValue)
{
box.Password = (string)e.NewValue;
}
box.PasswordChanged += PasswordBox_PasswordChanged;
}
private static void PasswordBox_PasswordChanged(object sender, RoutedEventArgs e)
{
var box = (PasswordBox)sender;
SetPassword(box, box.Password);
}
}
}
c#复制代码
/* VMod.cs */
using System.ComponentModel;
namespace MVVM.ViewModel
{
public class VMod: INotifyPropertyChanged
{
private string? _password;
public string? Password
{
get => _password;
set
{
if (_password == value) return;
_password = value;
OnPropertyChanged(nameof(Password));
}
}
public event PropertyChangedEventHandler? PropertyChanged;
protected void OnPropertyChanged(string name)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
}
}
}
