1、依赖属性
依赖属性使用效率更高的保存机制,并支持附加功能,如更改通知(change notification)以及属性值继承(在元素树中向下传播默认属性值的能力)。
依赖项属性也是WPF许多重要功能的基础,包括动画、数据绑定以及样式，在代码中仍可以使用与读取和设置传统的.NET属性相同的方式来读取和设置依赖项属性。
2、应用场景
1、要求属性支持绑定
2、自定义/拓展控件属性
3、支持验证/强制回调
4、属性继承
5、附加属性
3、依赖属性定义
VS当中使用propdp可创建依赖属性
public class Dp:DependencyObject{//定义public static readonly DependencyProperty AgeProperty;//注册static Dp(){//第一个参数为xaml当中应当显示的属性名称//第二个参数:该属性的类型//第三个参数:该属性所属类型//第四个参数:默认值AgeProperty = DependencyProperty.Register("Age",typeof(int),typeof(Dp),new PropertyMetadata(0));}//包装public int Age{get { return (int)GetValue(AgeProperty); }set { SetValue(AgeProperty, value); }}}
4、依赖属性值改变回调
在PropertyMetadata当中当中传入一个回调函数
public class Dp:Panel{//定义public static readonly DependencyProperty AgeProperty;//注册static Dp(){//第一个参数为xaml当中应当显示的属性名称//第二个参数:该属性的类型//第三个参数:该属性所属类型//第四个参数:默认值AgeProperty = DependencyProperty.Register("Age",typeof(int),typeof(Dp),new PropertyMetadata(0,OnAgeChange));}/// <summary>/// 改变回调函数/// </summary>/// <param name="d">发出该改变的依赖对象</param>/// <param name="e">发生的事件</param>private static void OnAgeChange(DependencyObject d, DependencyPropertyChangedEventArgs e){//业务代码//e.NewValue//e.OldValue }//包装public int Age{get { return (int)GetValue(AgeProperty); }set { SetValue(AgeProperty, value); }}}
5、依赖属性验证回调
在DependencyProperty.Register注册方法当中传入回调函数
public class Dp:Panel{//定义public static readonly DependencyProperty AgeProperty;//注册static Dp(){//第一个参数为xaml当中应当显示的属性名称//第二个参数:该属性的类型//第三个参数:该属性所属类型//第四个参数:默认值AgeProperty = DependencyProperty.Register("Age",typeof(int),typeof(Dp),new PropertyMetadata(0,OnAgeChange),new ValidateValueCallback(OnAgeChangeValid));}private static bool OnAgeChangeValid(object value){//验证逻辑return true;}//包装public int Age{get { return (int)GetValue(AgeProperty); }set { SetValue(AgeProperty, value); }}}
6、依赖属性的强制回调
在PropertyMetadata当中当中传入一个回调函数
static Dp(){//第一个参数为xaml当中应当显示的属性名称//第二个参数:该属性的类型//第三个参数:该属性所属类型//第四个参数:默认值AgeProperty = DependencyProperty.Register("Age",typeof(int),typeof(Dp),new PropertyMetadata(0,OnAgeChange,ForceCallBack),new ValidateValueCallback(OnAgeChangeValid));}
7、依赖属性继承
AgeProperty = DependencyProperty.Register("Age",typeof(int),typeof(Dp),new FrameworkPropertyMetadata(0,FrameworkPropertyMetadataOptions.Inherits), );
public class Class1:Control{public int StuAge{get { return (int)GetValue(StuAgeProperty); }set { SetValue(StuAgeProperty, value); }}// Using a DependencyProperty as the backing store for StuAge. This enables animation, styling, binding, etc...public static readonly DependencyProperty StuAgeProperty =DpTest.AgeProperty.AddOwner( typeof(Class1),new FrameworkPropertyMetadata("", FrameworkPropertyMetadataOptions.Inherits));}
8、附加属性
使用propa快捷键可快速创建
public class AttachTest{//包装public static int GetCustPwdProperty(DependencyObject obj){return (int)obj.GetValue(CustPwdProperty);}public static void SetCustPwdProperty(DependencyObject obj, int value){obj.SetValue(CustPwdProperty, value);}// 定义、注册public static readonly DependencyProperty CustPwdProperty =DependencyProperty.RegisterAttached("CustPwdProperty", typeof(string), typeof(AttachTest), new PropertyMetadata(""));}
<PasswordBox local:AttachTest.CustPwdProperty="{Binding Pwd}" Width="60" Height="30"></PasswordBox>
将PasswordBox与附加属性之间建立联系:
//附加属性public class AttachTest{//包装public static string GetCustPwdProperty(DependencyObject obj){return (string)obj.GetValue(CustPwdProperty);}public static void SetCustPwdProperty(DependencyObject obj, string value){obj.SetValue(CustPwdProperty, value);}// 定义、注册public static readonly DependencyProperty CustPwdProperty =DependencyProperty.RegisterAttached("CustPwdProperty", typeof(string), typeof(AttachTest), new PropertyMetadata("", OnCustPwdPropertyChanged));//当附加属性变化时将PasswordBox的Password修改为附加属性的值private static void OnCustPwdPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e){string pwd = (string)e.NewValue;PasswordBox passwordBox = d as PasswordBox;//弱转换if (passwordBox != null){passwordBox.Password = pwd;}}//当PasswordBox的Password变化时将附加属性修改为Password的值public static bool GetOrderProperty(DependencyObject obj){return (bool)obj.GetValue(OrderProperty);}public static void SetGetOrderProperty(DependencyObject obj, bool value){obj.SetValue(OrderProperty, value);}// Using a DependencyProperty as the backing store for MyProperty. This enables animation, styling, binding, etc...public static readonly DependencyProperty OrderProperty =DependencyProperty.RegisterAttached("OrderProperty", typeof(bool), typeof(AttachTest), new PropertyMetadata(true, OnOrderPropertyChanged));private static void OnOrderPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e){PasswordBox passwordBox = d as PasswordBox;if (passwordBox != null){passwordBox.PasswordChanged -= OnPasswordChanged;passwordBox.PasswordChanged += OnPasswordChanged;}}private static void OnPasswordChanged(object sender, RoutedEventArgs e){PasswordBox dp = sender as PasswordBox;SetCustPwdProperty(dp, dp.Password);}}