WPF DependencyProperty Validation Binding to the object property

Question

I am trying to create a validation rule for a given control (in this scenario, it is the TextBox).

I am not able to obtain a successful Binding to the property of an object, although appropriate steps were taken: ValidationRule and DepedencyProperty are taken advantage of.

Kindly find code below. A side note is that "Is Required" in the custom Validation class is always False, unless I explicitly set the value in the XAML (no Binding, as per "Is Ranged" parameter).

Any tips and suggestions are appreciated.

Thank you in advance :)

XAML Code:

<TextBox Style="{StaticResource ValidationError}" LostFocus="ForceValidationCheck"
         Visibility="{Binding Type, Converter={StaticResource Visibility}, ConverterParameter='Number'}"
         IsEnabled="{Binding RelativeSource={x:Static RelativeSource.Self}, Converter={StaticResource IsEnabled}}">
    <TextBox.Text>
        <Binding Path="Value">
            <Binding.ValidationRules>
                <validation:NumericValidation>
                    <validation:NumericValidation.Dependency>
                        <validation:NumericDependency IsRequired="{Binding Path=IsRequired}" IsRanged="True" Min="5"/>
                    </validation:NumericValidation.Dependency>
                </validation:NumericValidation>
            </Binding.ValidationRules>
        </Binding>
    </TextBox.Text>
</TextBox>

Validation Class:

public NumericDependency Dependency { get; set; }

public override ValidationResult Validate(object value, CultureInfo cultureInfo)
{
    isRequired = Dependency.IsRequired;
}

Validation Dependency Class:

public static readonly DependencyProperty IsRequiredProperty =
        DependencyProperty.Register("IsRequired", typeof(bool), typeof(NumericDependency), new UIPropertyMetadata(default(bool)));

public bool IsRequired
{
    get
    {
        return (bool) GetValue(IsRequiredProperty);
    }
    set
    {
        SetValue(IsRequiredProperty, value);
    }
}

Answer 1

You can use a proxy. It will allow you to bind a Property to your ValidationRule.

Proxy example

Here is a code sample that may help you :

<Utils:Proxy In="{Binding IsRequired, Mode=OneWay,UpdateSourceTrigger=PropertyChanged}" Out="{Binding ElementName=numericValidationRule, Path=IsRequired}" />
<TextBox>
    <TextBox.Text>
        <Binding Path="Value">
            <Binding.ValidationRules>
                <NumericValidation x:Name="numericValidationRule" />
            </Binding.ValidationRules>
        </Binding>
    </TextBox.Text>
</TextBox>