验证绑定第一次加载 [英] Validation Binding on First Load

问题描述

我仍然在WPF验证挣扎。

I'm still struggling with validation in WPF.

我有需要的文字出现在一个文本框，即它实施的强制性约束场自定义的验证规则。

I've got a custom validation rule which requires text to appear in a textbox i.e. it enforces a mandatory field constraint.

<TextBox local:Masking.Mask="^[a-zA-Z0-9]*$" x:Name="CameraIdCodeTextBox" Grid.Row="1" Grid.Column="1">
  <Binding Path="CameraIdCode" Mode="TwoWay" UpdateSourceTrigger="PropertyChanged" NotifyOnValidationError="True" ValidatesOnExceptions="True">
    <Binding.ValidationRules>
      <localValidation:RequiredFieldRule />
    </Binding.ValidationRules>
  </Binding>
</TextBox>

问题是，当窗口第一次加载，还有在TextBox中没有文本（如你所期望的）。但是文本属性被绑定到的视图模型的属性，因此，验证规则被烧成，指示不存在与窗口的问题。 - 用户甚至有机会违反业务规则之前

The problem is, that when the Window first loads, there is no text in the TextBox (as you would expect). But the Text property is being bound to a property on the ViewModel, and as such, the validation Rule is firing, indicating that there is a problem with the Window - before the user has even had an opportunity to violate a business rule.

这是其之前已经解决的问题？我不能一直去体验这个第一。我敢肯定，这是对年轻球员的一个陷阱。

Is this a problem which has been solved before? I can't have been the 1st to experience this. I'm sure it is a trap for young players.

推荐答案

这已经有一段时间，我应该已经更新了这个问题。我解决它使用一个类，我在WPF书发现由伊恩Griffths（O'Reilly的书）：

It's been a while and I should have updated this question. I resolved it using a class which I found in a WPF book by Ian Griffths (an O'Reilly book):

public static class Validator
{
    /// <summary>
    /// This method forces WPF to validate the child controls of the control passed in as a parameter.
    /// </summary>
    /// <param name="parent">Type: DependencyObject. The control which is the descendent root control to validate.</param>
    /// <returns>Type: bool. The validation result</returns>
    public static bool IsValid(DependencyObject parent)
    {
        // Validate all the bindings on the parent
        bool valid = true;
        LocalValueEnumerator localValues = parent.GetLocalValueEnumerator();
        while (localValues.MoveNext())
        {
            LocalValueEntry entry = localValues.Current;
            if (BindingOperations.IsDataBound(parent, entry.Property))
            {
                Binding binding = BindingOperations.GetBinding(parent, entry.Property);
                foreach (ValidationRule rule in binding.ValidationRules)
                {
                    ValidationResult result = rule.Validate(parent.GetValue(entry.Property), null);
                    if (!result.IsValid)
                    {
                        BindingExpression expression = BindingOperations.GetBindingExpression(parent, entry.Property);
                        Validation.MarkInvalid(expression, new ValidationError(rule, expression, result.ErrorContent, null));
                        valid = false;
                    }
                }
            }
        }

        // Validate all the bindings on the children
        for (int i = 0; i != VisualTreeHelper.GetChildrenCount(parent); ++i)
        {
            DependencyObject child = VisualTreeHelper.GetChild(parent, i);
            if (!IsValid(child))
            {
                valid = false;
            }
        }

        return valid;
    }

}

然后，在视图中，我有以下配置：

Then, on the view, I had the following configuration:

<TextBox local:Masking.Mask="^[0-9]*$" IsEnabled="{Binding Path=LocationNumberEnabled}" Grid.Row="1" Grid.Column="3">
    <Binding Path="LocationNumber"  Mode="TwoWay" UpdateSourceTrigger="LostFocus" NotifyOnValidationError="True" ValidatesOnExceptions="True">
        <Binding.ValidationRules>
            <localValidation:PositiveNumberRule />
            <localValidation:RequiredFieldRule />
        </Binding.ValidationRules>
    </Binding>                    
</TextBox>

工作就像一个魅力！我只是叫IsValid的方法，每次我想手动验证例如时间一个按钮preSS。

Worked like a charm! I just called the IsValid method every time I wanted to manually validate e.g. on a button press.

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