为什么会失败?
我有一个包含 ComboBox 的 UserControl。
我有一个名为“强制”的属性,如果没有选择,用户可以使用它添加验证。
所以我在用户控件中有这个:
public static DependencyProperty MandatoryProperty
= DependencyProperty.Register("Mandatory", typeof(bool), typeof(CountyPicker),
new PropertyMetadata((bool)false, OnChangedMandatoryByBinding));
private static void OnChangedMandatoryByBinding
(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var value = (bool)e.NewValue;
((CountyPicker)d).OnChangedMandatoryByBinding(value);
}
public bool Mandatory
{
get { return (bool)GetValue(MandatoryProperty); }
set { SetValue(MandatoryProperty, value); }
}
public void OnChangedMandatoryByBinding(bool value)
{
var binding = BindingOperations.GetBinding
(TheComboBox, ComboBox.SelectedItemProperty);
binding.ValidationRules.Clear();
if (value == true) // strange that I need this without getting a warning
{
binding.ValidationRules.Add(new NotNullValidator());
}
}
该 xaml 包含:
<UserControl x:Class="Foo.Controls.Pickers.CountyPicker"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ComboBox Name="TheComboBox"
KeyDown="TheComboBox_KeyDown"
SelectedItem="{Binding County,Mode=TwoWay}" />
</UserControl>
但是虽然 Mandatory 的值是这样设置的:
<p:CountyPicker Mandatory="True"
CountyCode="{Binding customer.CountyCode, Mode=TwoWay}"/>
...似乎没有进行验证。我在 NotNullValidator:s Validate 方法中设置了一个断点,但没有命中。