原文:

上一篇我们将大概做了个了解 ，这篇将继续学习WPF数据绑定的相关内容

数据源与控件的Binding

Binding作为数据传送UI的通道，通过INotityPropertyChanged接口的PropertyChanged事件通知Binding数据属性发生改变

public class Product : INotifyPropertyChanged  {      private string name;      public string Name      {          get { return name; }          set          {              name = value;              if (PropertyChanged != null)              {                  this.PropertyChanged.Invoke(this, new PropertyChangedEventArgs("Name"));              }          }      }      public event PropertyChangedEventHandler PropertyChanged;  }

通过Binding关联UI控件元素

this.txtOfProduct.SetBinding(TextBox.TextProperty, new Binding() { Path = new PropertyPath("Name"), Source = p });

控件之间的Binding

我们也可以通过后台C#代码实现

TextBox1.SetBinding(TextBox.TextProperty, new Binding("Value") { ElementName = "slider1", Mode=BindingMode.OneWay });

统计文本字符长度

Binding的Path

Path的索引器方式

当使用一个集合或者DataView作为Binding源时，如果我们想把它的默认元素作为Path来使用

List
    
      names = new List
     
      () { "张三", "李四", "王五" }; //张三 this.TextBox1.SetBinding(TextBox.TextProperty, new Binding("/") { Source = names }); //“张三”字符串的长度 this.TextBox2.SetBinding(TextBox.TextProperty, new Binding("/Length") { Source = names,Mode=BindingMode.OneWay}); //获取“张三”字符串中的第1个字符 this.TextBox3.SetBinding(TextBox.TextProperty, new Binding("/[0]") { Source = names, Mode = BindingMode.OneWay });
     
    

如果集合中嵌套集合，我们依然可以通过多级"/"语法把子集作为Path的元素

class City  {      public string Name { get; set; }  }  class Province  {      public List
    
      Citys { get; set; }      public string Name { get; set; }  }  class Country  {      public List
     
       Provinces { get; set; }      public string Name { get; set; }  }
     
    

TextBox1.SetBinding(TextBox.TextProperty, new Binding("/Name") { Source = countries });  TextBox2.SetBinding(TextBox.TextProperty, new Binding("/Provinces/Name") { Source = countries });  TextBox3.SetBinding(TextBox.TextProperty, new Binding("/Provinces/Citys/Name") { Source = countries });

省略Path

sys需要引用xmlns:sys="clr-namespace:System;assembly=mscorlib"

         
     
               WPF入门手册     
      
     
    

TextBox2.SetBinding(TextBox.TextProperty, new Binding(".") { Source = "WPF技术入门" });

没有Path和Source，Binding可以通过DataContext获取数据

         
     
               WPF入门手册     
      
     
    

选中ListBox元素显示对应的属性的一个例子

List
    
      cities = new List
     
      () {      new City() { Id=1,Name="北京" },      new City() { Id=2,Name="昆明" },      new City() { Id=3,Name="上海" },      new City() { Id=4,Name="厦门" },      new City() { Id=5,Name="广州" }  };  this.ListBox1.ItemsSource = cities;  this.ListBox1.DisplayMemberPath = "Name";  this.TextBox1.SetBinding(TextBox.TextProperty, new Binding("SelectedItem.Id") { Source = this.ListBox1 });
     
    

使用Binding的RelativeSource

当Binding有明确的数据源的时，我们可以通过Soure或ElementName赋值办法关联Binding,但有事我们不知道Soure对象的名字是什么，却知道它与作为Binding目标对象的UI元素布局上的相对关系,通过RelativeSourceMode枚举设置关联的对象关系

后台代码处理

RelativeSource rs = new RelativeSource(RelativeSourceMode.FindAncestor) {     AncestorLevel = 1,     AncestorType = typeof(StackPanel) }; //将StackPanel的Name s1赋给了TextBox1的Text TextBox1.SetBinding(TextBox.TextProperty, new Binding("Name") { RelativeSource = rs });

也可以通过XAML的方式赋值

Binding数据验证

Binding的ValidationRules属性的类型为Collection<ValidationRule>。通过实现Validate方法返回给ValidationResult对象，并设置IsVaild属性，ErrorContent属性可以接受一个字符串。

public class RangValidationRule : ValidationRule {     //验证数据     public override ValidationResult Validate(object value, CultureInfo cultureInfo)     {         double d = 0;         if (double.TryParse(value.ToString(), out d))         {             if (d >= 1 && d <= 100)             {                 return new ValidationResult(true, null);             }         }         return new ValidationResult(false, "数据错误");     } }

Binding binding = new Binding("Value") {     Source=slider1,     UpdateSourceTrigger=UpdateSourceTrigger.PropertyChanged, }; binding.ValidationRules.Add(new RangValidationRule()); this.TextBox1.SetBinding(TextBox.TextProperty, binding);

显示错误提示

public MainWindow()  {      InitializeComponent();      Binding binding = new Binding("Value")      {          Source = slider1,          UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged,          NotifyOnValidationError = true//开启错误通知      };      binding.ValidationRules.Add(new RangValidationRule());      this.TextBox1.SetBinding(TextBox.TextProperty, binding);       //注册验证错误事件      this.TextBox1.AddHandler(Validation.ErrorEvent, new RoutedEventHandler(ValidationErrorNotify));  }  private void ValidationErrorNotify(object sender, RoutedEventArgs e)  {      var errors = Validation.GetErrors(this.TextBox1);      if (errors.Count > 0)      {          TextBlock1.Text = errors[0].ErrorContent.ToString();      }  }

多路Binding

一般我们在做注册用户功能的时候，输入密码的时候都需要再确认输入密码，比较两次输入是否一致，现在我们可以通过多路Binding来简单的实现这个功能

首先实现一个IMultiValueConverter接口功能，如果两次密码一致，提交按钮状态为可用

public class SubmitMultiBindingConverter : IMultiValueConverter    {        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)        {            return (!values.Cast
    
     ().Any(a => string.IsNullOrEmpty(a))/*验证所有元素非空*/ &&                values[0].ToString() == values[1].ToString())/*值1=值2*/;                    }        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)        {            throw new NotImplementedException();        }    }
    

XAML代码

后台Binding

Binding pwdBinding = new Binding("Text") { Source = Password }; Binding pwderBinding = new Binding("Text") { Source = Passworder }; MultiBinding multi = new MultiBinding() { Mode=BindingMode.OneWay}; multi.Bindings.Add(pwdBinding); multi.Bindings.Add(pwderBinding); multi.Converter = new SubmitMultiBindingConverter(); Submit.SetBinding(Button.IsEnabledProperty, multi);

以上就是Binding常用到的功能，下篇我将继续学习依赖属性和WPF路由事件的相关内容