根据用户选择，在WPF中显示数字的小数位数。

huangapple
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英文:

show decimal places of number in WPF according to user selection

问题

我想在一个 WPF 窗口中显示一个 double 类型的数字。用户应该能够选择显示多少位小数。

我想在视图（XAML）中直接解决这个问题，而不是在代码后台中格式化数字。我尝试使用 StringFormat 和 MultiBinding 来显示绑定的数字，并选择显示的小数位数：

MainWindow.xaml:

  1. <Window x:Class="WpfApp1.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.     mc:Ignorable="d"
  7.     DataContext="{Binding RelativeSource={RelativeSource Self}}"
  8.     Width="400"  Height="100">
  10. <StackPanel Orientation="Horizontal" Height="30">
  12.     <TextBlock  Margin="5" >Precision:</TextBlock>
  13.     
  14.     <ComboBox x:Name="cbPrecision" 
  15.                 Margin="5" 
  16.                 MinWidth="80"
  17.                 ItemsSource="{Binding Path=DecimalPlaces}" 
  18.                 DisplayMemberPath="Value" 
  19.                 SelectedValuePath="Key"/>
  21.     <TextBlock Margin="5" >
  22.         <TextBlock.Text>
  23.             <MultiBinding StringFormat="Number: {0:N{1}}">
  24.                 <Binding Path="SomeNumber"/>
  25.                 <Binding Path="SelectedValue" ElementName="cbPrecision"/>
  26.             </MultiBinding>
  27.         </TextBlock.Text>
  28.     </TextBlock>
  30. </StackPanel>

MainWindow.xaml.cs:

  1. using System.Collections.Generic;
  2. using System.Windows;
  4. namespace WpfApp1
  5. {
  6.     public partial class MainWindow : Window
  7.     {
  9.         public MainWindow()
  10.         {
  11.             InitializeComponent();
  12.         }
  14.         public Dictionary<int, double> DecimalPlaces { get; } = new() {
  15.             { 0, 1 },
  16.             { 1, 0.1 },
  17.             { 2, 0.01 },
  18.             { 3, 0.001 }
  19.         };
  21.         public double SomeNumber { get; set; } = 123.45678;
  22.     }
  23. }

结果是 TextBox 根本没有显示出来：

根据用户选择，在WPF中显示数字的小数位数。

期望的结果是：

根据用户选择，在WPF中显示数字的小数位数。

观察：

可能是嵌套的字符串格式化有问题

  1. <MultiBinding StringFormat="Number: {0:N{1}}">

因为将包含 StringFormat 的代码行更改为

  1. <MultiBinding StringFormat="Number: {0:N4}-DecimalPlaces: {1}">

可以正确显示 TextBox 中的值：

根据用户选择，在WPF中显示数字的小数位数。

英文:

I want to display a number of type double in a WPF window. The user should be enabled to select how many decimal places should be displayed.

I want to solve this in the view (XAML) directly without formatting the number in code behind. I try to display the bound number with selected amount of decimal places using StringFormat and MultiBinding:

MainWindow.xaml:

  1. &lt;Window x:Class=&quot;WpfApp1.MainWindow&quot;
  2.     xmlns=&quot;http://schemas.microsoft.com/winfx/2006/xaml/presentation&quot;
  3.     xmlns:x=&quot;http://schemas.microsoft.com/winfx/2006/xaml&quot;
  4.     xmlns:d=&quot;http://schemas.microsoft.com/expression/blend/2008&quot;
  5.     xmlns:mc=&quot;http://schemas.openxmlformats.org/markup-compatibility/2006&quot;
  6.     mc:Ignorable=&quot;d&quot;
  7.     DataContext=&quot;{Binding RelativeSource={RelativeSource Self}}&quot;
  8.     Width=&quot;400&quot;  Height=&quot;100&quot;&gt;
  10. &lt;StackPanel Orientation=&quot;Horizontal&quot; Height=&quot;30&quot;&gt;
  12.     &lt;TextBlock  Margin=&quot;5&quot; &gt;Precision:&lt;/TextBlock&gt;
  13.     
  14.     &lt;ComboBox x:Name=&quot;cbPrecision&quot; 
  15.                 Margin=&quot;5&quot; 
  16.                 MinWidth=&quot;80&quot;
  17.                 ItemsSource=&quot;{Binding Path=DecimalPlaces}&quot; 
  18.                 DisplayMemberPath=&quot;Value&quot; 
  19.                 SelectedValuePath=&quot;Key&quot;/&gt;
  21.     &lt;TextBlock Margin=&quot;5&quot; &gt;
  22.         &lt;TextBlock.Text&gt;
  23.             &lt;MultiBinding StringFormat=&quot;Number: {0:N{1}}&quot;&gt;
  24.                 &lt;Binding Path=&quot;SomeNumber&quot;/&gt;
  25.                 &lt;Binding Path=&quot;SelectedValue&quot; ElementName=&quot;cbPrecision&quot;/&gt;
  26.             &lt;/MultiBinding&gt;
  27.         &lt;/TextBlock.Text&gt;
  28.     &lt;/TextBlock&gt;
  30. &lt;/StackPanel&gt;

</Window>

MainWindow.xaml.cs:

  1. using System.Collections.Generic;
  2. using System.Windows;
  4. namespace WpfApp1
  5. {
  6.     public partial class MainWindow : Window
  7.     {
  9.         public MainWindow()
  10.         {
  11.             InitializeComponent();
  12.         }
  14.         public Dictionary&lt;int, double&gt; DecimalPlaces { get; } = new() {
  15.             { 0, 1 },
  16.             { 1, 0.1 },
  17.             { 2, 0.01 },
  18.             { 3, 0.001 }
  19.         };
  21.         public double SomeNumber { get; set; } = 123.45678;
  22.     }
  23. }

As result the TextBox is not displayed at all:

根据用户选择，在WPF中显示数字的小数位数。

Expected result:

根据用户选择，在WPF中显示数字的小数位数。

Observation:

There must be some problem with the "nested" string formatting

  1. &lt;MultiBinding StringFormat=&quot;Number: {0:N{1}}&quot;&gt;

because changing the code line containing the StringFormat to

  1. &lt;MultiBinding StringFormat=&quot;Number: {0:N4}-DecimalPlaces: {1}&quot;&gt;

displays the values in the TextBox correctly:

根据用户选择，在WPF中显示数字的小数位数。

答案1

得分: 0

首先，将TextBlock替换为具有ContentStringFormat属性的Label。

然后，定义一个实现INotifyPropertyChanged接口的类。

具体的实现如下所示：

  2. // 在 Window_Loaded 中
  3. panel.DataContext = new PanelModel();
  5. class PanelModel : INotifyPropertyChanged
  6. {
  7.     public Dictionary<string, double> DecimalPlaces { get; } = new() {
  8.         { "N0", 1 },
  9.         { "N1", 0.1 },
  10.         { "N2", 0.01 },
  11.         { "N3", 0.001 },
  12.         { "N4", 0.0001 }
  13.     };
  15.     string _ContentFormat = "N0";
  16.     double _SomeNumber = 123.45678;
  18.     public string ContentFormat {
  19.         get => _ContentFormat;
  20.         set
  21.         {
  22.             if (value != _ContentFormat)
  23.             {
  24.                 _ContentFormat = value;
  25.                 OnPropertyChanged(nameof(ContentFormat));
  26.                 OnPropertyChanged(nameof(SomeNumber));
  27.             }
  28.         }
  29.     }
  31.     public double SomeNumber
  32.     {
  33.         get => _SomeNumber;
  34.         set
  35.         {
  36.             if (value != _SomeNumber)
  37.             {
  38.                 _SomeNumber = value;
  39.                 OnPropertyChanged(nameof(SomeNumber));
  40.             }
  41.         }
  42.     }
  44.     public event PropertyChangedEventHandler PropertyChanged;
  46.     protected void OnPropertyChanged(string propertyName)
  47.     {
  48.         PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
  49.     }
  50. }

我尝试将comboBox1.SelectedValue绑定到ContentStringFormat，但它不起作用。

因此，我使用了INotifyPropertyChanged接口，并在ContentFormat更改时触发了SomeNumber的通知。

  1. <StackPanel x:Name="panel" Orientation="Horizontal">
  3.     <Label Content="Precision: " />
  5.     <ComboBox x:Name="comboBox1"
  6.                 ItemsSource="{Binding Path=DecimalPlaces}"
  7.                 DisplayMemberPath="Value"
  8.                 SelectedValuePath="Key"
  9.                 SelectedValue="{Binding Path=ContentFormat}"
  10.                 VerticalContentAlignment="Center"
  11.                 Width="120"/>
  13.     <TextBox Text="{Binding Path=SomeNumber, UpdateSourceTrigger=PropertyChanged}"
  14.              Width="120"
  15.              Margin="15,0"/>
  17.     <Label x:Name="labelSomeNumber"
  18.             Content="{Binding Path=SomeNumber}"
  19.             ContentStringFormat="{Binding Path=ContentFormat}" />
  21. </StackPanel>
英文:

First, replace TextBlock with Label, which has a ContentStringFormat property for binding.

Then, define a class that implements the INotifyPropertyChanged interface.

The specific implementation is as follows:

  2. // in Window_Loaded
  3. panel.DataContext = new PanelModel();
  5. class PanelModel : INotifyPropertyChanged
  6. {
  7.     public Dictionary&lt;string, double&gt; DecimalPlaces { get; } = new() {
  8.         { &quot;N0&quot;, 1 },
  9.         { &quot;N1&quot;, 0.1 },
  10.         { &quot;N2&quot;, 0.01 },
  11.         { &quot;N3&quot;, 0.001 },
  12.         { &quot;N4&quot;, 0.0001 }
  13.     };
  15.     string _ContentFormat = &quot;N0&quot;;
  16.     double _SomeNumber = 123.45678;
  18.     public string ContentFormat {
  19.         get =&gt; _ContentFormat;
  20.         set
  21.         {
  22.             if (value != _ContentFormat)
  23.             {
  24.                 _ContentFormat = value;
  25.                 OnPropertyChanged(nameof(ContentFormat));
  26.                 OnPropertyChanged(nameof(SomeNumber));
  27.             }
  28.         }
  29.     }
  31.     public double SomeNumber
  32.     {
  33.         get =&gt; _SomeNumber;
  34.         set
  35.         {
  36.             if (value != _SomeNumber)
  37.             {
  38.                 _SomeNumber = value;
  39.                 OnPropertyChanged(nameof(SomeNumber));
  40.             }
  41.         }
  42.     }
  44.     public event PropertyChangedEventHandler PropertyChanged;
  46.     protected void OnPropertyChanged(string propertyName)
  47.     {
  48.         PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
  49.     }
  50. }

I tried to bind comboBox1.SelectedValue to ContentStringFormat, but it doesn't work.

So, I used the INotifyPropertyChanged interface and triggered the SomeNumber Changed notification when ContentFormat changes.

  1. &lt;StackPanel x:Name=&quot;panel&quot; Orientation=&quot;Horizontal&quot;&gt;
  3.     &lt;Label Content=&quot;Precision: &quot; /&gt;
  5.     &lt;ComboBox x:Name=&quot;comboBox1&quot;
  6.                 ItemsSource=&quot;{Binding Path=DecimalPlaces}&quot;
  7.                 DisplayMemberPath=&quot;Value&quot;
  8.                 SelectedValuePath=&quot;Key&quot;
  9.                 SelectedValue=&quot;{Binding Path=ContentFormat}&quot;
  10.                 VerticalContentAlignment=&quot;Center&quot;
  11.                 Width=&quot;120&quot;/&gt;
  13.     &lt;TextBox Text=&quot;{Binding Path=SomeNumber, UpdateSourceTrigger=PropertyChanged}&quot;
  14.              Width=&quot;120&quot;
  15.              Margin=&quot;15,0&quot;/&gt;
  17.     &lt;Label x:Name=&quot;labelSomeNumber&quot;
  18.             Content=&quot;{Binding Path=SomeNumber}&quot;
  19.             ContentStringFormat=&quot;{Binding Path=ContentFormat}&quot; /&gt;
  21. &lt;/StackPanel&gt;

答案2

得分: 0

以下是翻译好的内容：

根据Clemens的评论，我创建了一个转换器。完整的解决方案：

MainWindow.xaml：

  1. <Window x:Class="WpfApp1.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.     mc:Ignorable="d"
  7.     xmlns:local="clr-namespace:WpfApp1"
  8.     DataContext="{Binding RelativeSource={RelativeSource Self}}"
  9.     Width="400" Height="100">
  11. <StackPanel Orientation="Horizontal" Height="30">
  13.     <TextBlock Margin="5" >Precision:</TextBlock>
  14.     
  15.     <ComboBox x:Name="cbPrecision" 
  16.                 Margin="5" 
  17.                 MinWidth="80"
  18.                 ItemsSource="{Binding Path=DecimalPlaces}" 
  19.                 DisplayMemberPath="Value" 
  20.                 SelectedValuePath="Key"/>
  22.     <TextBlock Margin="5" >
  23.         <TextBlock.Text>
  24.             <MultiBinding>
  25.                 <MultiBinding.Converter>
  26.                     <local:DecimalPlacesConverter />
  27.                 </MultiBinding.Converter>
  28.                 <Binding Path="SomeNumber"/>
  29.                 <Binding Path="SelectedValue" ElementName="cbPrecision"/>
  30.             </MultiBinding>
  31.         </TextBlock.Text>
  32.     </TextBlock> 
  33. </StackPanel>

MainWindow.xaml.cs:

  1. public partial class MainWindow : Window
  2. {
  3.     public MainWindow()
  4.     {
  5.         InitializeComponent();
  6.     }
  7.     public Dictionary<int, double> DecimalPlaces { get; } = new() {
  8.         { 0, 1 },
  9.         { 1, 0.1 },
  10.         { 2, 0.01 },
  11.         { 3, 0.001 }
  12.     };
  13.     public double SomeNumber { get; set; } = 123.45678;
  14. }

DecimalPlacesConverter.cs:

  1. public class DecimalPlacesConverter : IMultiValueConverter
  2. {
  3.     public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
  4.     {
  5.         try
  6.         {
  7.             return Math.Round((double)values[0], (int)values[1]).ToString("N" + values[1]);
  8.         }
  9.         catch (Exception)
  10.         {
  11.             return double.NaN;
  12.         }
  13.     }
  15.     public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
  16.     {
  17.         throw new NotImplementedException();
  18.     }
  19. }
英文:

Following Clemens comment I created a converter. Complete solution:

MainWindow.xaml:

  1. &lt;Window x:Class=&quot;WpfApp1.MainWindow&quot;
  2.     xmlns=&quot;http://schemas.microsoft.com/winfx/2006/xaml/presentation&quot;
  3.     xmlns:x=&quot;http://schemas.microsoft.com/winfx/2006/xaml&quot;
  4.     xmlns:d=&quot;http://schemas.microsoft.com/expression/blend/2008&quot;
  5.     xmlns:mc=&quot;http://schemas.openxmlformats.org/markup-compatibility/2006&quot;
  6.     mc:Ignorable=&quot;d&quot;
  7.     xmlns:local=&quot;clr-namespace:WpfApp1&quot;
  8.     DataContext=&quot;{Binding RelativeSource={RelativeSource Self}}&quot;
  9.     Width=&quot;400&quot;  Height=&quot;100&quot;&gt;
  11. &lt;StackPanel Orientation=&quot;Horizontal&quot; Height=&quot;30&quot;&gt;
  13.     &lt;TextBlock  Margin=&quot;5&quot; &gt;Precision:&lt;/TextBlock&gt;
  14.     
  15.     &lt;ComboBox x:Name=&quot;cbPrecision&quot; 
  16.                 Margin=&quot;5&quot; 
  17.                 MinWidth=&quot;80&quot;
  18.                 ItemsSource=&quot;{Binding Path=DecimalPlaces}&quot; 
  19.                 DisplayMemberPath=&quot;Value&quot; 
  20.                 SelectedValuePath=&quot;Key&quot;/&gt;
  22.     &lt;TextBlock Margin=&quot;5&quot; &gt;
  23.         &lt;TextBlock.Text&gt;
  24.             &lt;MultiBinding&gt;
  25.                 &lt;MultiBinding.Converter&gt;
  26.                     &lt;local:DecimalPlacesConverter /&gt;
  27.                 &lt;/MultiBinding.Converter&gt;
  28.                 &lt;Binding Path=&quot;SomeNumber&quot;/&gt;
  29.                 &lt;Binding Path=&quot;SelectedValue&quot; ElementName=&quot;cbPrecision&quot;/&gt;
  30.             &lt;/MultiBinding&gt;
  31.         &lt;/TextBlock.Text&gt;
  32.     &lt;/TextBlock&gt; 
  33. &lt;/StackPanel&gt;

</Window>

MainWindow.xaml.cs:
<!-- language: c# -->
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
public Dictionary<int, double> DecimalPlaces { get; } = new() {
{ 0, 1 },
{ 1, 0.1 },
{ 2, 0.01 },
{ 3, 0.001 }
};
public double SomeNumber { get; set; } = 123.45678;
}

DecimalPlacesConverter.cs:
<!-- language: c# -->
public class DecimalPlacesConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
try
{
return Math.Round((double)values[0], (int)values1).ToString("N" + values1);
}
catch (Exception)
{
return double.NaN;
}
}

  1.     public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
  2.     {
  3.         throw new NotImplementedException();
  4.     }
  5. }

huangapple
  • 本文由 发表于 2023年8月9日 16:28:19
  • 转载请务必保留本文链接：https://go.coder-hub.com/76865906.html
  • data-binding
  • string-formatting
  • wpf
  • xaml
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