WPF入门：数据绑定

上一篇我们将XAML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

 <TextBox x:Name="TextBox1" Text="{Binding ElementName=slider1,Path=Value,Mode=OneWay}"></TextBox>
 <Slider x:Name="slider1" Margin="5"></Slider>

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

 <TextBox x:Name="TextBox1"  Margin="5"  TextWrapping="Wrap" ></TextBox>
 <TextBlock Margin="5"  TextAlignment="Right" Text="{Binding ElementName=TextBox1, Path=Text.Length}"></TextBlock>

Binding的Path

Path的索引器方式

  <TextBox x:Name="TextBox1"  Margin="5"  TextWrapping="Wrap" ></TextBox>
  <!--获取Text的第三个字符-->
  <TextBlock Margin="5"  TextAlignment="Right" Text="{Binding ElementName=TextBox1, Path=Text.[2]}"></TextBlock>
  <TextBlock Margin="5"  TextAlignment="Right" Text="{Binding ElementName=TextBox1, Path=Text[2]}"></TextBlock>

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<string> names = new List<string>() { "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<City> Citys { get; set; }
      public string Name { get; set; }
  }

  class Country
  {
      public List<Province> 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"

 <StackPanel.Resources>
     <sys:String x:Key="text">
         WPF入门手册
     </sys:String>
 </StackPanel.Resources>
 <TextBox x:Name="TextBox1"  Margin="5" Text="{Binding .,Source={StaticResource ResourceKey=text}}" ></TextBox>

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

 <StackPanel.DataContext>
     <sys:String>
         WPF入门手册
     </sys:String>
 </StackPanel.DataContext>
 <TextBox x:Name="TextBox1"  Margin="5" Text="{Binding Mode=OneWay}" ></TextBox>

选中ListBox元素显示对应的属性的一个例子

 <TextBox x:Name="TextBox1"  Margin="5" ></TextBox>
 <ListBox x:Name="ListBox1"></ListBox>

  List<City> cities = new List<City>() {
      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

<Grid x:Name="g1">
    <StackPanel x:Name="s1">
        <DockPanel x:Name="d1">
            <TextBox x:Name="TextBox1"  Margin="5" ></TextBox>
        </DockPanel>
    </StackPanel>
</Grid>

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

    <Grid x:Name="g1">
        <StackPanel x:Name="s1">
            <DockPanel x:Name="d1">
                <TextBox x:Name="TextBox1"  Margin="5" Text="{Binding RelativeSource={RelativeSource AncestorType={x:Type DockPanel},AncestorLevel=1,Mode=FindAncestor}, Path=Name}" ></TextBox>
            </DockPanel>
        </StackPanel>
    </Grid>

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");
     }
 }

 <TextBox x:Name="TextBox1" Margin="5"></TextBox>
 <Slider x:Name="slider1" Minimum="1" Maximum="100" Margin="5"></Slider>

 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<string>().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

 <TextBox x:Name="Password" Margin="5"></TextBox>
 <TextBox x:Name="Passworder" Margin="5"></TextBox>
 <Button x:Name="Submit" Content="提交" Margin="10" Height="30" Width="100"></Button>

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