WPF ValidationRule 加载控件时验证

Question

我有一个带有此验证的控件

<MyPicker.SelectedItem>
 <Binding Path="Person.Value" Mode="TwoWay" UpdateSourceTrigger="PropertyChanged" NotifyOnValidationError="True">
  <Binding.ValidationRules>
   <rules:MyValidationRule ValidationType="notnull"/>
  </Binding.ValidationRules>
 </Binding>
</MyPicker.SelectedItem>

这是验证类:

class MyValidationRule : ValidationRule
{        
 private string _validationType;
 public string ValidationType
 {
  get { return _validationType; }
  set { _validationType = value;  }
 }

 public override ValidationResult Validate(object value, CultureInfo cultureInfo)
 {            
  ValidationResult trueResult = new ValidationResult(true, null);

  switch (_validationType.ToLower())
  {
   case "notnull": return value == null ? new ValidationResult(false, "EMPTY FIELD") : trueResult;               
   default: return trueResult;
  }
 }
}

问题:当属性更改时，将调用 Validate( ) 方法，这是正确的。

但是要在创建 MyControl 时一开始就调用此方法吗？如果控件中存在空值，我需要在初始化后立即证明(并显示验证错误)

Answer 1

好的，我已经解决了:当元素与简单属性绑定(bind)时强制进行验证 - ValidatesOnTargetUpdated:

 <rules:MyValidationRule ValidatesOnTargetUpdated="True"  ValidationType="notnull"/>