使用WPF专注于验证错误

如何解决使用WPF专注于验证错误

我有一个小型应用程序，其中有一个通过MVVM绑定到模型的文本框：

我的模特：

public class MyModel : INotifyPropertyChanged
{
    private double _myValue = 0;

    public event PropertyChangedEventHandler PropertyChanged;

    public double MyValue 
    {
        get => _myValue;
        set
        {
            if(value != _myValue)
            {
                if (value == 4)
                    throw new InvalidOperationException();
                _myValue = value;
                OnPropertyChanged();
            }
        }
    }

    /// <summary>
    /// Called when a property was changed.
    /// </summary>
    /// <param name="propertyName">Name of the affected property.</param>
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this,new PropertyChangedEventArgs(propertyName));
    }
}

我的视图如下：

<Window x:Class="ValidationTests.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:ValidationTests"
        mc:Ignorable="d"
        Title="MainWindow" Height="201.696" Width="322.679">
    
    <Window.Resources>
        <Style TargetType="TextBox" BasedOn="{StaticResource {x:Type 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>
    </Window.Resources>
    
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <TextBox Grid.Row="0" Text="{Binding MyValue,Mode=TwoWay,ValidatesOnExceptions=True}" 
                 HorizontalAlignment="Center" Width="150" VerticalAlignment="Center"/>
        <Button Grid.Row="1" HorizontalAlignment="Center" Width="100" VerticalAlignment="Center" Height="30" Content="Test"/>
    </Grid>
</Window>

现在，当发生验证错误时，我想将重点放在文本框上。我该如何实现？这种风格有可能吗？

解决方法

如果要防止键盘焦点在TextBox包含有效值之前丢失，可以使用附加行为或直接在视图中处理PreviewLostKeyboardFocus事件：>

private void TextBox_PreviewLostKeyboardFocus(object sender,KeyboardFocusChangedEventArgs e) =>
    e.Handled = Validation.GetHasError((TextBox)sender);

您还应该将UpdateSourceTrigger设置为PropertyChanged以在丢失焦点之前执行验证：

<TextBox Text="{Binding MyValue,UpdateSourceTrigger=PropertyChanged,ValidatesOnExceptions=True}" 
         HorizontalAlignment="Center" Width="150" VerticalAlignment="Center"
         PreviewLostKeyboardFocus="TextBox_PreviewLostKeyboardFocus"/>

您不能使用Style或其他方式在纯XAML中实现此功能。