背水一战 Windows 10 (18) - 绑定: 与 Element 绑定, 与 Indexer 绑定, TargetNullValue, FallbackValue...

<Pagex:Class="Windows10.Bind.BindingElement"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:local="using:Windows10.Bind"xmlns:d="http://schemas.microsoft.com/expression/blend/2008"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"mc:Ignorable="d"><Grid Background="Transparent"><StackPanel Margin="10 0 10 10"><!--本例用于演示如何与 Element 绑定，以及 OneTime, OneWay, TwoWay 的区别--><!--OneTime 方式绑定元素--><TextBox Text="{Binding ElementName=txtOneTime, Path=Text, Mode=OneTime}" /><TextBox Name="txtOneTime" Text="OneTime" Margin="0 10 0 0" /><!--OneWay 方式绑定元素（OneWay 是默认方式）--><TextBox Text="{Binding ElementName=txtOneWay, Path=Text, Mode=OneWay}" Margin="0 30 0 0" /><TextBox Name="txtOneWay" Text="OneWay" Margin="0 10 0 0" /><!--TwoWay 方式绑定元素（同时演示一下 Binding 标记的另一种写法，就是直接把 Path 指定的路径放到 Binding 的后面）--><TextBox Text="{Binding Text, ElementName=txtTwoWay, Mode=TwoWay}" Margin="0 30 0 0" /><TextBox Name="txtTwoWay" Text="TwoWay" Margin="0 10 0 0" /><!--TwoWay 方式绑定元素（在 C# 端指定 Binding 对象的方式一）--><TextBox Name="textBox1" Margin="0 30 0 0" /><TextBox Name="textBox2" Text="TwoWay" Margin="0 10 0 0" /><!--TwoWay 方式绑定元素（在 C# 端指定 Binding 对象的方式二）--><TextBox Name="textBox3" Margin="0 30 0 0" /><TextBox Name="textBox4" Text="TwoWay" Margin="0 10 0 0" /></StackPanel></Grid>
</Page>

/** 演示如何与 Element 绑定*/using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Data;namespace Windows10.Bind
{public sealed partial class BindingElement : Page{public BindingElement(){this.InitializeComponent();SetBindingDemo1();SetBindingDemo2();}// 在 C# 端做绑定（方式一）private void SetBindingDemo1(){// 实例化 Binding 对象Binding binding = new Binding(){ElementName = nameof(textBox2),Path = new PropertyPath(nameof(TextBox.Text)),Mode = BindingMode.TwoWay // 默认是 OneWay 的
            };// 将目标对象的目标属性与指定的 Binding 对象关联
            BindingOperations.SetBinding(textBox1, TextBox.TextProperty, binding);}// 在 C# 端做绑定（方式二）private void SetBindingDemo2(){// 实例化 Binding 对象Binding binding = new Binding(){ElementName = nameof(textBox4),Path = new PropertyPath(nameof(TextBox.Text)),Mode = BindingMode.TwoWay // 默认是 OneWay 的
            };// 将目标对象的目标属性与指定的 Binding 对象关联
            textBox3.SetBinding(TextBox.TextProperty, binding);}}
}

<Pagex:Class="Windows10.Bind.BindingIndexer"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:local="using:Windows10.Bind"xmlns:d="http://schemas.microsoft.com/expression/blend/2008"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"mc:Ignorable="d"><Grid Background="Transparent"><StackPanel Margin="10 0 10 10"><!--演示如何绑定集合中的某个元素--><TextBlock Name="textBlock" Text="{Binding Path=[3]}" /><!--演示如何绑定集合中的某个对象的某个属性--><TextBlock Name="textBlock2" Text="{Binding Path=[5].Name}" Margin="0 10 0 0" /><!--演示如何绑定 string 类型的索引器--><TextBlock Name="textBlock3" Text="{Binding Path=[webabcd]}" Margin="0 10 0 0" /><!--演示如何绑定字典表中指定 key 的数据--><TextBlock Name="textBlock4" Text="{Binding Path=[hello]}" Margin="0 10 0 0" /><!--演示如何在 C# 端绑定索引器--><TextBox Name="textBox" Margin="0 10 0 0" /></StackPanel></Grid>
</Page>

/** 演示如何与 Indexer 绑定*/using System;
using System.Collections.Generic;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Data;
using Windows10.Common;namespace Windows10.Bind
{public sealed partial class BindingIndexer : Page{public BindingIndexer(){this.InitializeComponent();this.Loaded += BindingIndexer_Loaded;BindingDemo();}private void BindingIndexer_Loaded(object sender, RoutedEventArgs e){// 用于演示如何绑定集合中的某个元素List<string> list = new List<string>();for (int i = 0; i < 10; i++){list.Add("索引：" + i.ToString());}textBlock.DataContext = list;// 用于演示如何绑定集合中的某个对象的某个属性textBlock2.DataContext = TestData.GetEmployees();// 用于演示如何绑定 string 类型的索引器textBlock3.DataContext = this;// 用于演示如何绑定字典表中指定 key 的数据Dictionary<string, string> dic = new Dictionary<string, string>() { { "hello", "hello webabcd" } };textBlock4.DataContext = dic;}// 自定义一个索引器public object this[string indexer]{get{return "string: " + indexer;}}// 在 C# 端绑定索引器private void BindingDemo(){textBox.DataContext = this;// 实例化 Binding 对象Binding binding = new Binding(){Path = new PropertyPath("[wanglei]")};// 将目标对象的目标属性与指定的 Binding 对象关联
            BindingOperations.SetBinding(textBox, TextBox.TextProperty, binding);/** 注：经测试在 TextBox 做如上绑定是正常的。但是如果在 TextBlock 做如上绑定则运行时报错 Attempted to read or write protected memory. This is often an indication that other memory is corrupt. 不知道为什么*/}}
}

<Pagex:Class="Windows10.Bind.TargetNullValueFallbackValue"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:local="using:Windows10.Bind"xmlns:d="http://schemas.microsoft.com/expression/blend/2008"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"mc:Ignorable="d"><Grid Background="Transparent"><StackPanel Margin="10 0 10 10"><!--FallbackValue - 当绑定失败时显示的值--><TextBlock Name="textBlock1" Text="{Binding Path=MyName, FallbackValue='绑定失败时的默认值'}" Margin="5" /><!--TargetNullValue - 当绑定数据为 null 时显示的值--><TextBlock Name="textBlock2" Text="{Binding Path=MyName, TargetNullValue='绑定数据的返回值为 null'}" Margin="5" /></StackPanel></Grid>
</Page>

/** 演示 Binding 中的 TargetNullValue 和 FallbackValue 的用法*/using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;namespace Windows10.Bind
{public sealed partial class TargetNullValueFallbackValue : Page{public TargetNullValueFallbackValue(){this.InitializeComponent();}protected override void OnNavigatedTo(NavigationEventArgs e){// 为 textBlock2 提供数据上下文textBlock2.DataContext = this;/*// 实例化 Binding 对象Binding binding = new Binding(){Path = new PropertyPath("Name"),TargetNullValue = "TargetNullValue",FallbackValue = "FallbackValue"};// 将目标对象的目标属性与指定的 Binding 对象关联BindingOperations.SetBinding(textBlock2, TextBox.TextProperty, binding);*/}public string MyName { get; set; } = null;}
}