背水一戰(zhàn) Windows 10 (20) - 綁定: DataContextChanged, UpdateSourceTrigger, 對(duì)綁定的數(shù)據(jù)做自定義轉(zhuǎn)換 原文:背水一戰(zhàn) Windows 10 (20) - 綁定: DataContextChanged, UpdateSourceTrigger, 對(duì)綁定的數(shù)據(jù)做自定義轉(zhuǎn)換

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背水一戰(zhàn) Windows 10 (20) - 綁定: DataContextChanged, UpdateSourceTrigger, 對(duì)綁定的數(shù)據(jù)做自定義轉(zhuǎn)換

作者：webabcd


介紹
背水一戰(zhàn) Windows 10 之?綁定

• DataContextChanged - FrameworkElement 的 DataContext 發(fā)生變化時(shí)觸發(fā)的事件
• UpdateSourceTrigger - 數(shù)據(jù)更新的觸發(fā)方式
• 對(duì)綁定的數(shù)據(jù)做自定義轉(zhuǎn)換

示例
1、演示 DataContextChanged?的用法
Bind/DataContextChanged.xaml

<Pagex:Class="Windows10.Bind.DataContextChanged"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"><TextBlock Name="lblMsg" Margin="5" /><Button x:Name="btnChange" Content="改變 listBox 的數(shù)據(jù)上下文" Click="btnChange_Click" Margin="5" /><ListBox x:Name="listBox" ItemsSource="{Binding}" DataContextChanged="listBox_DataContextChanged" Background="Orange" Margin="5" /></StackPanel></Grid> </Page>

Bind/DataContextChanged.xaml.cs

/** DataContextChanged - FrameworkElement 的 DataContext 發(fā)生變化時(shí)觸發(fā)的事件*/using System; using System.Collections.Generic; using Windows.UI.Xaml; using Windows.UI.Xaml.Controls;namespace Windows10.Bind {public sealed partial class DataContextChanged : Page{public DataContextChanged(){this.InitializeComponent();this.Loaded += DataContextChanged_Loaded;}private void DataContextChanged_Loaded(object sender, RoutedEventArgs e){// 指定數(shù)據(jù)上下文listBox.DataContext = new List<string> { "a", "b", "c" };}private void btnChange_Click(object sender, RoutedEventArgs e){// 修改數(shù)據(jù)上下文listBox.DataContext = new List<string> { "a", "b", new Random().Next(0, 1000).ToString().PadLeft(3, '0') };}private void listBox_DataContextChanged(FrameworkElement sender, DataContextChangedEventArgs args){/** FrameworkElement.DataContextChanged - 數(shù)據(jù)上下文發(fā)生改變后觸發(fā)的事件*/// 數(shù)據(jù)上下文發(fā)生改變后lblMsg.Text = "數(shù)據(jù)上下文發(fā)生改變：" + DateTime.Now.ToString("hh:mm:ss");}} }

2、演示 UpdateSourceTrigger?的用法
Bind/UpdateSourceTrigger.xaml

<Pagex:Class="Windows10.Bind.UpdateSourceTrigger"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"><TextBlock Name="lblMsg" Foreground="Orange" Margin="5" /><!--UpdateSourceTrigger - 數(shù)據(jù)更新的觸發(fā)方式Default - 失去焦點(diǎn)后觸發(fā)PropertyChanged - 屬性值發(fā)生改變后觸發(fā)Explicit - 需要通過(guò) BindingExpression.UpdateSource() 顯示觸發(fā)--><TextBox Text="{Binding Text, Mode=TwoWay, ElementName=lblMsg, UpdateSourceTrigger=Default}" Margin="5" /><TextBox Text="{Binding Text, Mode=TwoWay, ElementName=lblMsg, UpdateSourceTrigger=PropertyChanged}" Margin="5" /><TextBox Name="txtExplicit" Text="{Binding Text, Mode=TwoWay, ElementName=lblMsg, UpdateSourceTrigger=Explicit}" Margin="5" /><Button Name="btnBinding" Content="顯示觸發(fā)更新" Click="btnBinding_Click" Margin="5" /></StackPanel></Grid> </Page>

Bind/UpdateSourceTrigger.xaml.cs

/** UpdateSourceTrigger - 數(shù)據(jù)更新的觸發(fā)方式* Default - 失去焦點(diǎn)后觸發(fā)* PropertyChanged - 屬性值發(fā)生改變后觸發(fā)* Explicit - 需要通過(guò) BindingExpression.UpdateSource() 顯示觸發(fā)* * * BindingExpression - 綁定信息，可以通過(guò) FrameworkElement 的 GetBindingExpression() 方法獲取指定屬性的綁定信息* DataItem - 獲取綁定的源對(duì)象* ParentBinding - 獲取綁定的 Binding 對(duì)象（Binding 對(duì)象里包括 ElementName, Path, Mode 等綁定信息）* UpdateSource() - 將當(dāng)前值發(fā)送到 TwoWay 綁定的源對(duì)象的綁定的屬性中*/using System; using Windows.UI.Popups; using Windows.UI.Xaml; using Windows.UI.Xaml.Controls; using Windows.UI.Xaml.Data;namespace Windows10.Bind {public sealed partial class UpdateSourceTrigger : Page{public UpdateSourceTrigger(){this.InitializeComponent();}private async void btnBinding_Click(object sender, RoutedEventArgs e){// 顯示觸發(fā) txtExplicit 的數(shù)據(jù)更新BindingExpression be = txtExplicit.GetBindingExpression(TextBox.TextProperty);be.UpdateSource();// 獲取綁定的相關(guān)信息Binding binding = be.ParentBinding;TextBlock textBlock = be.DataItem as TextBlock;MessageDialog messageDialog = new MessageDialog($"BindingExpression.DataItem:{textBlock.Name}, Binding.Mode:{binding.Mode}");await messageDialog.ShowAsync();}} }

3、演示如何對(duì)綁定的數(shù)據(jù)做自定義轉(zhuǎn)換
Bind/BindingConverter.xaml

<Pagex:Class="Windows10.Bind.BindingConverter"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"><!--配置 IValueConverter 資源--><StackPanel.Resources><local:IntegerLetterConverter x:Key="IntegerLetterConverter"/><local:FormatConverter x:Key="FormatConverter"/><x:String x:Key="FormatString">格式化字符串 {0}</x:String></StackPanel.Resources><Slider Name="slider1" Minimum="97" Maximum="122" Value="1" Width="300" Background="White" HorizontalAlignment="Left" Margin="5" /><!--演示如何使用 Binding 的 Converter, ConverterParameter, ConverterLanguage注：ConverterParameter 和 ConverterLanguage 不支持綁定，只能配置為一個(gè)靜態(tài)的值（但是在 C# 端可以實(shí)現(xiàn)一些在 xaml 中無(wú)法實(shí)現(xiàn)的特性，詳見(jiàn)后面的例子）--><TextBox Name="textBox1" Width="300" HorizontalAlignment="Left" Margin="5"Text="{Binding ElementName=slider1, Path=Value, Mode=TwoWay,Converter={StaticResource IntegerLetterConverter},ConverterParameter=param, ConverterLanguage=zh}" /><Slider Name="slider2" Minimum="97" Maximum="122" Value="1" Width="300" Background="White" HorizontalAlignment="Left" Margin="5" /><!--在 C# 端使用 Binding 的 Converter, ConverterParameter, ConverterLanguage--><TextBox Name="textBox2" Width="300" HorizontalAlignment="Left" Margin="5" /><TextBlock Name="lblMsg" Margin="5" TextWrapping="Wrap" /><!--演示如何在 ConverterParameter 中通過(guò) {0} 格式化字符串 --><TextBlock Name="textBlock1" Text="我是“textBlock1”" Margin="5" /><TextBlock Name="textBlock2" Margin="5" Text="{Binding ElementName=textBlock1, Path=Text,Converter={StaticResource FormatConverter},ConverterParameter={StaticResource FormatString}}" /></StackPanel></Grid> </Page>

Bind/BindingConverter.xaml.cs

/** 演示如何對(duì)綁定的數(shù)據(jù)做自定義轉(zhuǎn)換*/using System; using Windows.UI.Xaml; using Windows.UI.Xaml.Controls; using Windows.UI.Xaml.Data;namespace Windows10.Bind {public sealed partial class BindingConverter : Page{public BindingConverter(){this.InitializeComponent();this.Loaded += BindingConverter_Loaded;}private void BindingConverter_Loaded(object sender, RoutedEventArgs e){// 實(shí)例化 Binding 對(duì)象Binding binding = new Binding(){ElementName = nameof(slider2),Path = new PropertyPath(nameof(Slider.Value)),Mode = BindingMode.TwoWay, // 默認(rèn)是 OneWay 的Converter = new IntegerLetterConverter(),ConverterParameter = lblMsg, // 將 ConverterParameter 設(shè)置為一個(gè)指定的控件，這個(gè)在 xaml 中實(shí)現(xiàn)不了，但是可以在 C# 端實(shí)現(xiàn)ConverterLanguage = "zh"};// 將目標(biāo)對(duì)象的目標(biāo)屬性與指定的 Binding 對(duì)象關(guān)聯(lián) BindingOperations.SetBinding(textBox2, TextBox.TextProperty, binding);}}// 自定義一個(gè)實(shí)現(xiàn)了 IValueConverter 接口的類(lèi)，用于對(duì)綁定的數(shù)據(jù)做自定義轉(zhuǎn)換public sealed class IntegerLetterConverter : IValueConverter{/// <summary>/// 正向轉(zhuǎn)換器。將值從數(shù)據(jù)源傳給綁定目標(biāo)時(shí)，數(shù)據(jù)綁定引擎會(huì)調(diào)用此方法/// </summary>/// <param name="value">轉(zhuǎn)換之前的值</param>/// <param name="targetType">轉(zhuǎn)換之后的數(shù)據(jù)類(lèi)型</param>/// <param name="parameter">轉(zhuǎn)換器所使用的參數(shù)（它是通過(guò) Binding 的 ConverterParameter 傳遞過(guò)來(lái)的）</param>/// <param name="language">轉(zhuǎn)換器所使用的區(qū)域信息（它是通過(guò) Binding 的 ConverterLanguage 傳遞過(guò)來(lái)的）</param>/// <returns>轉(zhuǎn)換后的值</returns>public object Convert(object value, Type targetType, object parameter, string language){if (parameter != null && parameter.GetType() == typeof(TextBlock)){((TextBlock)parameter).Text = $"value: {value}, targetType: {targetType}, parameter: {parameter}, language: {language}";}int v = (int)(double)value;return (char)v;}/// <summary>/// 反向轉(zhuǎn)換器。將值從綁定目標(biāo)傳給數(shù)據(jù)源時(shí)，數(shù)據(jù)綁定引擎會(huì)調(diào)用此方法/// </summary>/// <param name="value">轉(zhuǎn)換之前的值</param>/// <param name="targetType">轉(zhuǎn)換之后的數(shù)據(jù)類(lèi)型</param>/// <param name="parameter">轉(zhuǎn)換器所使用的參數(shù)（它是通過(guò) Binding 的 ConverterParameter 傳遞過(guò)來(lái)的）</param>/// <param name="language">轉(zhuǎn)換器所使用的區(qū)域信息（它是通過(guò) Binding 的 ConverterLanguage 傳遞過(guò)來(lái)的）</param>/// <returns>轉(zhuǎn)換后的值</returns>public object ConvertBack(object value, Type targetType, object parameter, string language){if (parameter != null && parameter.GetType() == typeof(TextBlock)){((TextBlock)parameter).Text = $"value: {value}, targetType: {targetType}, parameter: {parameter}, language: {language}";}int v = ((string)value).ToCharArray()[0];return v;}}// 自定義一個(gè)實(shí)現(xiàn)了 IValueConverter 接口的類(lèi)，用于格式化字符串public sealed class FormatConverter : IValueConverter{public object Convert(object value, Type targetType, object parameter, string language){string format = (string)parameter;return string.Format(format, value);}public object ConvertBack(object value, Type targetType, object parameter, string language){throw new NotImplementedException();}} }

OK
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posted on 2017-09-21 10:05 NET未來(lái)之路 閱讀(...) 評(píng)論(...) 編輯 收藏

轉(zhuǎn)載于:https://www.cnblogs.com/lonelyxmas/p/7567069.html

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