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WPF数据转换_wpf 数字字符串绑定转换

作者：你好赵伟 | 2024-08-04 15:54:58

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wpf 数字字符串绑定转换

在基本绑定中，信息从源到目标的传递过程中没有任何变化。这看起来是符合逻辑的，但我们并不总是希望出现这种行为。通常，数据源使用的是低级表达方式，我们可能不希望直接在用户界面使用这种低级表达方式。WPF提供了两个工具，来进行数据转换：

字符串格式化

通过设置 Binding.StringFormat 属性对文本形式的数据进行转换——例如包含日期和数字的字符串。

值转换器

该功能更强大，使用该功能可以将任意类型的源数据转换为任意类型的对象表示，然后可以传递到关联的控件。

使用StringFormat属性

  1. <TextBlock Grid.Row="0" Grid.Column="0" Text="{Binding Path=Price, StringFormat=ConvertDirectly:{0:C}}"></TextBlock>
  2. <TextBox   Grid.Row="0" Grid.Column="1" Text="{Binding Path=Price, StringFormat={}{0:C}}"></TextBox>
  3. <TextBox   Grid.Row="2" Grid.Column="1" Text="{Binding Path=OrderDate, StringFormat={}{0:s}}"></TextBox>

可以看到后面两个StringFormat属性以花括号 {} 开头，完整值是 {}{0:C}，而不是 {0:C}，第一个则只有 {0:C}，这是因为在StringFormat 值以花括号开头时需要 {} 转义序列。

使用值转换器

为创建子转换器需要执行以下四个步骤：

1、创建一个实现IValueConverter接口的类

2、为该类声明添加ValueConversion特性，并指定目标数据类型

3、实现Convert()方法，该方法将数据从原来的格式转换为显示的格式

4、实现ConvertBack()方法，该方法执行反向变换，将值从显示格式转换为原格式

  1. [ValueConversion(typeof(decimal), typeof(string))]
  2. public class PriceConverter : IValueConverter
  3. {
  4.     public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
  5.     {
  6.         decimal price = (decimal)value;
  7.         return price.ToString("C", culture);
  8.     }
  9.     public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
  10.     {
  11.         string price = (string)value;
  12.         if (decimal.TryParse(price, System.Globalization.NumberStyles.Any, culture, out decimal result))
  13.         {
  14.             return result;
  15.         }
  16.         return value;
  17.     }
  18. }

要使用这个转换器，可以将其添加到页面的资源下，然后使用 Binding.Converter 指定。

  1. <Window>
  2.     <Window.Resources>
  3.         <local:PriceConverter x:Key="priceConverter"/>
  4.         <local:PriceToBackgroundConverter x:Key="priceToBackgroundConverter" MinimumPriceToHighlight="100" DefaultBrush="{x:Null}" HighlightBrush="Orange"/>
  5.         <local:ImagePathConverter x:Key="imagePathConverter"/>
  6.         <local:MultiValueConverter x:Key="multiValueConverter"/>
  7.     </Window.Resources>
  8.     <TextBox Text="{Binding Path=Price, Converter={StaticResource priceConverter}}"></TextBox>
  9. </Window>

多重绑定

可以将多个字段绑定到同一个输出控件，可以通过 StringFormat 或 MultiBinding.Converter 来格式化数据。多重绑定的值转换器需要实现的接口是 IMultiValueConverter，与 IValueConverter 接口比较类似，只是转换函数的第一个参数改成了数组形式。

  1.         <TextBlock Grid.Row="4" Grid.Column="0">
  2.             <TextBlock.Text>
  3.                 <MultiBinding StringFormat="{}{0}, {1}, {2}">
  4.                     <Binding Path="Price"/>
  5.                     <Binding Path="OrderDate"/>
  6.                     <Binding Path="Volume"/>
  7.                 </MultiBinding>
  8.             </TextBlock.Text>
  9.         </TextBlock>
  10.         <TextBlock Grid.Row="5" Grid.Column="0">
  11.             <TextBlock.Text>
  12.                 <MultiBinding Converter="{StaticResource multiValueConverter}">
  13.                     <Binding Path="Price"/>
  14.                     <Binding Path="Volume"/>
  15.                 </MultiBinding>
  16.             </TextBlock.Text>
  17.         </TextBlock>
  1. public class MultiValueConverter : IMultiValueConverter
  2. {
  3.     public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
  4.     {
  5.         decimal price = (decimal)values[0];
  6.         int volume = (int)values[1];
  7.         return (price * volume).ToString("C");
  8.     }
  9.     public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
  10.     {
  11.         throw new NotSupportedException();
  12.     }
  13. }

完整代码如下：

MainWindow.xaml

  1. <Window x:Class="TestDataConverter.MainWindow"
  2.         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  3.         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  4.         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
  5.         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
  6.         xmlns:local="clr-namespace:TestDataConverter"
  7.         mc:Ignorable="d"
  8.         Title="MainWindow" Height="450" Width="800">
  9.     <Window.Resources>
  10.         <local:PriceConverter x:Key="priceConverter"/>
  11.         <local:PriceToBackgroundConverter x:Key="priceToBackgroundConverter" MinimumPriceToHighlight="100" DefaultBrush="{x:Null}" HighlightBrush="Orange"/>
  12.         <local:ImagePathConverter x:Key="imagePathConverter"/>
  13.         <local:MultiValueConverter x:Key="multiValueConverter"/>
  14.     </Window.Resources>
  15.     <Grid Name="myGrid" Background="{Binding Path=Price, Converter={StaticResource priceToBackgroundConverter}}">
  16.         <Grid.ColumnDefinitions>
  17.             <ColumnDefinition/>
  18.             <ColumnDefinition/>
  19.         </Grid.ColumnDefinitions>
  20.         <Grid.RowDefinitions>
  21.             <RowDefinition/>
  22.             <RowDefinition/>
  23.             <RowDefinition/>
  24.             <RowDefinition/>
  25.             <RowDefinition/>
  26.             <RowDefinition/>
  27.         </Grid.RowDefinitions>
  28.  
  29.         <TextBlock Grid.Row="0" Grid.Column="0" Text="{Binding Path=Price, StringFormat=ConvertDirectly:{0:C}}"></TextBlock>
  30.         <TextBox   Grid.Row="0" Grid.Column="1" Text="{Binding Path=Price, StringFormat={}{0:C}}"></TextBox>
  31.  
  32.         <TextBlock Grid.Row="1" Grid.Column="0">ConvertWithConverter:</TextBlock>
  33.         <TextBox   Grid.Row="1" Grid.Column="1" Text="{Binding Path=Price, Converter={StaticResource priceConverter}}"></TextBox>
  34.  
  35.         <TextBlock Grid.Row="2" Grid.Column="0">ConvertDateTime:</TextBlock>
  36.         <TextBox   Grid.Row="2" Grid.Column="1" Text="{Binding Path=OrderDate, StringFormat={}{0:s}}"></TextBox>
  37.  
  38.         <TextBlock Grid.Row="3" Grid.Column="0">ConvertImagePath:</TextBlock>
  39.         <Image   Grid.Row="3" Grid.Column="1" Stretch="None" HorizontalAlignment="Left" Source="{Binding Path=Image, Converter={StaticResource imagePathConverter}}"></Image>
  40.  
  41.         <TextBlock Grid.Row="4" Grid.Column="0">
  42.             <TextBlock.Text>
  43.                 <MultiBinding StringFormat="{}{0}, {1}, {2}">
  44.                     <Binding Path="Price"/>
  45.                     <Binding Path="OrderDate"/>
  46.                     <Binding Path="Volume"/>
  47.                 </MultiBinding>
  48.             </TextBlock.Text>
  49.         </TextBlock>
  50.         <TextBlock Grid.Row="5" Grid.Column="0">
  51.             <TextBlock.Text>
  52.                 <MultiBinding Converter="{StaticResource multiValueConverter}">
  53.                     <Binding Path="Price"/>
  54.                     <Binding Path="Volume"/>
  55.                 </MultiBinding>
  56.             </TextBlock.Text>
  57.         </TextBlock>
  58.     </Grid>
  59. </Window>

MainWindow.xaml.cs

  1. using System;
  2. using System.Collections.Generic;
  3. using System.ComponentModel;
  4. using System.Globalization;
  5. using System.IO;
  6. using System.Runtime.CompilerServices;
  7. using System.Windows;
  8. using System.Windows.Controls;
  9. using System.Windows.Data;
  10. using System.Windows.Media;
  11. using System.Windows.Media.Imaging;
  12.  
  13. namespace TestDataConverter;
  14.  
  15. public class ViewModelBase : INotifyPropertyChanged
  16. {
  17.     public event PropertyChangedEventHandler? PropertyChanged;
  18.     protected virtual void OnPropertyChanged([CallerMemberName] string? propertyName = null)
  19.     {
  20.         PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
  21.     }
  22.     protected virtual bool SetProperty<T>(ref T member, T value, [CallerMemberName] string? propertyName = null)
  23.     {
  24.         if (EqualityComparer<T>.Default.Equals(member, value))
  25.         {
  26.             return false;
  27.         }
  28.         member = value;
  29.         OnPropertyChanged(propertyName);
  30.         return true;
  31.     }
  32. }
  33.  
  34. public class Order : ViewModelBase
  35. {
  36.     public decimal price = 0;
  37.     public decimal Price { get => price; set => SetProperty(ref price, value); }
  38.     public int volume = 0;
  39.     public int Volume { get => volume; set => SetProperty(ref volume, value); }
  40.  
  41.     public DateTime orderDate = DateTime.Now;
  42.     public DateTime OrderDate { get => orderDate; set => SetProperty(ref orderDate, value); }
  43.  
  44.     public string image = string.Empty;
  45.     public string Image { get => image; set => SetProperty(ref image, value); }
  46. }
  47. [ValueConversion(typeof(decimal), typeof(string))]
  48. public class PriceConverter : IValueConverter
  49. {
  50.     public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
  51.     {
  52.         decimal price = (decimal)value;
  53.         return price.ToString("C", culture);
  54.     }
  55.     public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
  56.     {
  57.         string price = (string)value;
  58.         if (decimal.TryParse(price, System.Globalization.NumberStyles.Any, culture, out decimal result))
  59.         {
  60.             return result;
  61.         }
  62.         return value;
  63.     }
  64. }
  65. [ValueConversion(typeof(decimal), typeof(Brush))]
  66. public class PriceToBackgroundConverter : IValueConverter
  67. {
  68.     public decimal MinimumPriceToHighlight { get; set; }
  69.     public Brush HighlightBrush { get; set; }
  70.     public Brush DefaultBrush { get; set; }
  71.  
  72.     public object Convert(object value, Type targetType, object parameter,
  73.       System.Globalization.CultureInfo culture)
  74.     {
  75.         decimal price = (decimal)value;
  76.         if (price >= MinimumPriceToHighlight)
  77.             return HighlightBrush;
  78.         else
  79.             return DefaultBrush;
  80.     }
  81.     public object ConvertBack(object value, Type targetType, object parameter,
  82.       System.Globalization.CultureInfo culture)
  83.     {
  84.         throw new NotSupportedException();
  85.     }
  86. }
  87. public class ImagePathConverter : IValueConverter
  88. {
  89.     private string imageDirectory = Directory.GetCurrentDirectory();
  90.     public string ImageDirectory
  91.     {
  92.         get { return imageDirectory; }
  93.         set { imageDirectory = value; }
  94.     }
  95.     public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
  96.     {
  97.         string imagePath = Path.Combine(ImageDirectory, (string)value);
  98.         return new BitmapImage(new Uri(imagePath));
  99.     }
  100.     public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
  101.     {
  102.         throw new NotSupportedException("The method or operation is not implemented.");
  103.     }
  104. }
  105. public class MultiValueConverter : IMultiValueConverter
  106. {
  107.     public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
  108.     {
  109.         decimal price = (decimal)values[0];
  110.         int volume = (int)values[1];
  111.         return (price * volume).ToString("C");
  112.     }
  113.     public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
  114.     {
  115.         throw new NotSupportedException();
  116.     }
  117. }
  118.  
  119. public partial class MainWindow : Window
  120. {
  121.     public MainWindow()
  122.     {
  123.         InitializeComponent();
  124.         myGrid.DataContext = Order;
  125.  
  126.         Order.Price = 100;
  127.         Order.Volume = 10;
  128.         Order.OrderDate = DateTime.Now;
  129.         Order.Image = "image1.gif";
  130.     }
  131.     public Order Order = new Order();
  132.  
  133.     private void Button_Click(object sender, RoutedEventArgs e)
  134.     {
  135.         Console.WriteLine("");
  136.     }
  137. }

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