World War I Windows 10 (20) and World War I windows

World War I Windows 10 (20) and World War I windows

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Backwater world war I Windows 10 (20)-binding: DataContextChanged, UpdateSourceTrigger, custom conversion of bound data

Author: webabcd


Introduction
Bind to Windows 10

• Events triggered when the DataContext of DataContextChanged-FrameworkElement changes
• UpdateSourceTrigger-data update trigger Method
• Perform custom conversion on bound data

Example
1. Demonstrate DataContextChanged usage
Bind/DataContextChanged. xaml

<Page x: 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"> <TextBlock Name = "lblMsg" Margin = "5"/> <button x: name = "btnChange" Content = "change the data context of listBox" 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

/** Events triggered when the DataContext of DataContextChanged-FrameworkElement changes */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) {// specify the data context listBox. dataContext = new List <string> {"a", "B", "c" };} private void btnChange_Click (object sender, RoutedEventArgs e) {// modify the data context 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-the event triggered when the data context changes * // lblMsg after the data context changes. text = "data context changed:" + DateTime. now. toString ("hh: mm: ss ");}}}

2. Demonstrate UpdateSourceTrigger usage
Bind/UpdateSourceTrigger. xaml

<Page x: 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"> <TextBlock Name = "lblMsg" Foreground = "Orange" Margin =" 5 "/> <! -- UpdateSourceTrigger-data update trigger method Default-triggers PropertyChanged when the focus is lost-triggers Explicit when the attribute value changes-BindingExpression is required. updateSource () display trigger --> <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 =" display trigger Update "Click =" btnBinding_Click "Margin =" 5 "/> </ stackPanel> </Grid> </Page>

Bind/UpdateSourceTrigger. xaml. cs

/** UpdateSourceTrigger-trigger Method of Data Update * Default-trigger * PropertyChanged when the focus is lost-trigger * Explicit after the attribute value is changed-BindingExpression is required. updateSource () display trigger */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 void btnBinding_Click (object sender, RoutedEventArgs e) {// display the data update BindingExpression that triggers txtExplicit. be = txtExplicit. getBindingExpression (TextBox. textProperty); be. updateSource ();}}}

3. demonstrate how to perform custom conversion on the bound data
Bind/BindingConverter. xaml

<Page x: 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 "> <! -- Configure IValueConverter resources --> <StackPanel. resources> <local: IntegerLetterConverter x: Key = "IntegerLetterConverter"/> </StackPanel. resources> <Slider Name = "slider1" Minimum = "97" Maximum = "122" Value = "1" Width = "300" Background = "White" HorizontalAlignment = "Left" Margin = "5"/> <! -- Demonstrate how to use the Converter, ConverterParameter, and ConverterLanguage of Binding. Note: ConverterParameter and ConverterLanguage do not support Binding, only one static value can be configured (but some features that cannot be implemented in xaml can be implemented in the C # end. For details, refer to the example below) --> <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"/> <! -- Use the Converter, ConverterParameter, and, converterLanguage --> <TextBox Name = "textBox2" Width = "300" HorizontalAlignment = "Left" Margin = "5"/> <TextBlock Name = "lblMsg" TextWrapping = "Wrap "/> </StackPanel> </Grid> </Page>

Bind/BindingConverter. xaml. cs

/** Demonstrate how to customize the conversion of bound data */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) {// instantiate the Binding object Binding binding = New Binding () {ElementName = nameof (slider2), Path = new PropertyPath (nameof (Slider. value), Mode = BindingMode. twoWay, // The default value is OneWay's Converter = new IntegerLetterConverter (), ConverterParameter = lblMsg, // set ConverterParameter to a specified control, which cannot be implemented in xaml, however, ConverterLanguage = "zh"} can be implemented in C #; // associate the target object's target attribute with the specified Binding object BindingOperations. setBinding (textBox2, TextBox. textProperty, bindin G) ;}} // customize a class that implements the IValueConverter interface, which is used to customize the conversion of bound data to public sealed class IntegerLetterConverter: IValueConverter {// <summary> // forward converter. When you pass the value from the data source to the bound destination, the Data Binding engine calls this method /// </summary> /// <param name = "value"> value before conversion </param> /// <param name = "targetType"> converted data type </param> // The parameter used by the <param name = "parameter"> converter (it is passed through the ConverterParameter of the Binding) </param> // <param name = "language"> region information used by the converter (it is transmitted through the ConverterLanguage of Binding) </param> // <returns> converted value </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> /// reverse converter. When you pass a value from the bound destination to the data source, the Data Binding engine calls this method /// </summary> /// <param name = "value"> value before conversion </param> /// <param name = "targetType"> converted data type </param> // The parameter used by the <param name = "parameter"> converter (it is passed through the ConverterParameter of the Binding) </param> // <param name = "language"> region information used by the converter (it is transmitted through the ConverterLanguage of Binding) </param> // <returns> converted value </returns> public object ConvertBack (object value, Type targetType, object parame Ter, 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 ;}}}

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