wpf - 通过验证绑定(bind)到双字段

Question

我正在尝试使用 UpdateSourceTrigger=PropertyChanged 将 TextBox 绑定(bind)到某个对象的 double 属性。目标是在编辑期间立即验证输入的值是否在允许的范围内(如果不在则显示错误)。我想在模型级别实现验证，即通过 IDataErrorInfo。

当我绑定(bind)到 int 属性时，一切都很好，但如果属性是 double ，则会出现令人沮丧的编辑行为:删除数字小数部分的最后一个有效数字后 - 小数分隔符会自动删除(带有所有可能的小数零)。例如，从数字“12.03”中删除数字“3”后，文本将更改为“12”而不是“12.0”。

请帮忙。

这里是示例代码:

MainWindow.xaml:

<Window x:Class="BindWithValidation.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="80" Width="200" WindowStartupLocation="CenterOwner">

  <StackPanel>
    <TextBox Width="100" Margin="10" Text="{Binding DoubleField, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}">
      <TextBox.Style>
        <Style TargetType="TextBox">
          <Style.Triggers>
            <Trigger Property="Validation.HasError" Value="true">
              <Setter Property="ToolTip" Value="{Binding RelativeSource={RelativeSource Self}, Path=(Validation.Errors)[0].ErrorContent}"/>
            </Trigger>
          </Style.Triggers>
        </Style>
      </TextBox.Style>
    </TextBox>
  </StackPanel>
</Window>

MainWindow.xaml.cs:

namespace BindWithValidation
{
  public partial class MainWindow : Window
  {
    private UISimpleData _uiData = new UISimpleData();

    public MainWindow()
    {
      InitializeComponent();
      DataContext = _uiData;
    }
  }
}

UISimpleData.cs:

namespace BindWithValidation
{
  public class UISimpleData : INotifyPropertyChanged, IDataErrorInfo
  {
    private double _doubleField = 12.03;

    public double DoubleField
    {
      get
      {
        return _doubleField;
      }
      set
      {
        if (_doubleField == value)
          return;

        _doubleField = value;
        RaisePropertyChanged("DoubleField");
      }
    }

    public string this[string propertyName]
    {
      get
      {
        string validationResult = null;
        switch (propertyName)
        {
          case "DoubleField":
          {
            if (DoubleField < 2 || DoubleField > 5)
              validationResult = "DoubleField is out of range";
            break;
          }

          default:
            throw new ApplicationException("Unknown Property being validated on UIData");
        }

        return validationResult;
      }
    }

    public string Error { get { return "not implemented"; } }

    public event PropertyChangedEventHandler PropertyChanged;

    protected void RaisePropertyChanged(string property)
    {
      if ( PropertyChanged != null )
        PropertyChanged(this, new PropertyChangedEventArgs(property)); 
    }
  }
}

Answer 1

The behavior of binding float values to a textbox has been changed from .NET 4 to 4.5. With .NET 4.5 it is no longer possible to enter a separator character (comma or dot) with ‘UpdateSourceTrigger = PropertyChanged’ by default.

Microsoft says, this (is) intended

If you still want to use ‘UpdateSourceTrigger = PropertyChanged’, you can force the .NET 4 behavior in your .NET 4.5 application by adding the following line of code to the constructor of your App.xaml.cs:

public App()  
{
    System.Windows.FrameworkCompatibilityPreferences
               .KeepTextBoxDisplaySynchronizedWithTextProperty = false;   
}

(Sebastian Lux - 从 here 逐字复制)