c# - WPF 中文本框的条件验证规则？

Question

我有一个 WPF 应用程序，其 UI 包含一个复选框和一个文本框。复选框和文本框绑定(bind)到我的业务对象的属性。我一直在使用验证规则来验证用户输入，并且在大多数情况下，它们非常简单(检查值是否不为 null/空，检查值是否在特定范围内，等等)。 FWIW，这是我现有的 XAML:

<StackPanel>
    <CheckBox x:Name="requirePinNumberCheckBox" IsChecked="{Binding Path=RequirePinNumber, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">Require PIN number</CheckBox>
    <TextBox x:Name="pinNumberTextBox" Style="{StaticResource textBoxInError}" PreviewTextInput="pinNumberTextBox_PreviewTextInput">
        <TextBox.Text>
            <Binding Path="PinNumber" Mode="TwoWay" UpdateSourceTrigger="LostFocus">
                <Binding.ValidationRules>
                    <local:PinNumberValidationRule ValidationStep="RawProposedValue"/>
                </Binding.ValidationRules>
            </Binding>
        </TextBox.Text>
    </TextBox>
</StackPanel>

我对文本框的验证规则很简单:

public class PinNumberValidationRule : ValidationRule
{
    public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo)
    {
        // make sure that the PIN number isn't blank
        if (string.IsNullOrEmpty(value.ToString()))
        {
            return new ValidationResult(false, "PIN number cannot be blank.");
        }
        else
        {
            return new ValidationResult(true, null);
        }
    }
}

与我的大多数其他验证方案不同，文本框的 ValidationRule 应该仅在复选框被选中时应用(或者更确切地说，当复选框绑定(bind)到的 bool 属性设置为 TRUE 时)。谁能告诉我如何实现这样的东西？谢谢!

Answer 1

您应该将验证逻辑从 UI (ValidationRule) 移开，并考虑在您的 ViewModel 中实现 IDataErrorInfo。

一个好的开始是 this article .

然后你可以这样做:

<StackPanel>
    <CheckBox x:Name="requirePinNumberCheckBox" IsChecked="{Binding Path=RequirePinNumber, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">Require PIN number</CheckBox>
    <TextBox x:Name="pinNumberTextBox" 
             PreviewTextInput="pinNumberTextBox_PreviewTextInput"
             Text="{Binding PinNumber, ValidatesOnDataErrors=True}"
             ToolTip="{Binding (Validation.Errors).CurrentItem.ErrorContent, RelativeSource={RelativeSource Self}}" />
</StackPanel>

   public class ViewModel : IDataErrorInfo, INotifyPropertyChanged
    {
            private bool _requirePinNumber;
            public bool RequirePinNumber
            {
                get
                {
                    return this._requirePinNumber;
                }
                set
                {
                    this._requirePinNumber = value;
                    if (this.PropertyChanged != null)
                    {
                        this.PropertyChanged(this, new PropertyChangedEventArgs("RequirePinNumber"));
                        this.PropertyChanged(this, new PropertyChangedEventArgs("PinNumber"));
                    }
                }
            }

            private string _pinNumber;
            public string PinNumber 
            { 
                get
                {
                    return this._pinNumber;
                }
                set
                {
                    this._pinNumber = value;
                    if (this.PropertyChanged != null)
                    {
                        this.PropertyChanged(this, new PropertyChangedEventArgs("PinNumber"));
                    }
                }
            }

            public string Error
            {
                get 
                { 
                    throw new NotImplementedException(); 
                }
            }

            public string this[string columnName]
            {
                get 
                {
                    if (columnName == "PinNumber") 
                    {
                        if (this.RequirePinNumber && string.IsNullOrEmpty(this.PinNumber))
                        {
                            return "PIN number cannot be blank.";
                        }
                    }
                    return string.Empty;
                }
            }

            public event PropertyChangedEventHandler PropertyChanged;
        }