WPF DataBinding验证被忽略

Question

我(相信)我正在以教科书的方式连接数据绑定验证,但它根本不起作用.

在调试器中,Validate(object value, CultureInfo cultureInfo)永远不会调用该方法.

是什么赋予了？此外,对于奖励积分,调试WPF的任何指针都会很棒.

我发布了我的XAML和有问题的课程

<UserControl x:Class="FooControl"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:local="clr-namespace:Foo.Controls"
         mc:Ignorable="d" 
         d:DesignWidth="300">
<Grid Name="GridFoo">
    <Grid.Resources>
        <local:ValueConverter x:Key="MyConverter" />
    </Grid.Resources>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*" />
        <ColumnDefinition Width="Auto" />
    </Grid.ColumnDefinitions>
    <TextBox Name="TextBoxScalar" Grid.Column="0" TextAlignment="Right">
        <TextBox.Text>
            <Binding Mode="OneWay" Path="Scalar" NotifyOnValidationError="True" ValidatesOnDataErrors="True" ValidatesOnExceptions="True">
                <Binding.ValidationRules>
                    <local:ScalarValidationRule />
                </Binding.ValidationRules>
            </Binding>
        </TextBox.Text>
    </TextBox>
    <TextBlock Name="TextBlockUnit" Grid.Column="1" TextAlignment="Left" Padding="3">
        <Hyperlink>
            <!-- Use a custom converter here b/c generics break wpf... -->
            <Run Text="{Binding Mode=OneWay, Path=Unit, Converter={StaticResource MyConverter}}" />
        </Hyperlink>
    </TextBlock>
</Grid>

有效性规则

public class ScalarValidationRule : ValidationRule
{
    public override ValidationResult Validate(object value, CultureInfo cultureInfo)
    {
        string number = value as string;
        double d;
        return new ValidationResult(Double.TryParse(number, NumberStyles.Any, cultureInfo, out d),
            String.Format("\"{0}\" is not a number.", number));
    }
}

Answer 1

您正在将ValidationRule添加到单向绑定中.单向绑定永远不会将值推送到源,因此无需验证任何内容,并且永远不会调用ValidationRule.如果要验证用户输入的数据,请Mode="TwoWay"在绑定上进行设置.您还可以完全省略Mode属性,因为TextBox.Text默认绑定为双向.

如果您确实需要单向绑定,并且希望在将值从源(Scalar)推送到目标(TextBox.Text)时进行验证,则在ValidationRule上将ValidatesOnTargetUpdated设置为True.您可以在XAML中或在ValidationRule类的构造函数中执行此操作.