BlockType属性条件验证咨询：仅DisplayPdfButton为真时必填DownloadPdfText

Absolutely, this is totally achievable! Since you're working with EPiServer (I can tell from the TabNames reference), here are a couple of robust approaches to implement this conditional required validation for your Block Type:

Approach 1: Custom Validation Attribute #

Create a reusable custom validation attribute that checks the value of a dependent property before enforcing required validation on your target property.

Step 1: Implement the Custom Attribute #

[AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
public class ConditionalRequiredAttribute : ValidationAttribute
{
    // Name of the property we're checking against
    public string DependentProperty { get; set; }
    // The value the dependent property needs to match to trigger required validation
    public object TargetValue { get; set; }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        // Get the dependent property from the Block Type
        var dependentProperty = validationContext.ObjectType.GetProperty(DependentProperty);
        if (dependentProperty == null)
        {
            return new ValidationResult($"Could not find dependent property: {DependentProperty}");
        }

        // Get the current value of the dependent property
        var dependentValue = dependentProperty.GetValue(validationContext.ObjectInstance, null);

        // If the dependent property matches our target value AND the target property is empty, return an error
        if (Equals(dependentValue, TargetValue) && (value == null || string.IsNullOrWhiteSpace(value.ToString())))
        {
            return new ValidationResult(FormatErrorMessage(validationContext.DisplayName));
        }

        // Validation passes
        return ValidationResult.Success;
    }
}

Step 2: Update Your Block Type #

Replace the [Required] attribute on DownloadPdfText with your new custom attribute, pointing to the DisplayPdfButton property:

[CultureSpecific]
[Display(Name = "Display PDF Button", GroupName = TabNames.PDFCustomisation, Order = 0)]
public virtual bool DisplayPdfButton { get; set; }

[CultureSpecific]
[ConditionalRequired(
    DependentProperty = nameof(DisplayPdfButton), 
    TargetValue = true, 
    ErrorMessage = "Download Pdf Text is required when Display PDF Button is enabled.")]
[Display(Name = "Download Pdf Text", GroupName = TabNames.PDFCustomisation, Order = 1)]
public virtual string DownloadPdfText { get; set; }

Approach 2: EPiServer IValidate Interface #

EPiServer has a built-in validation interface IValidate<T> that's perfect for type-specific validation logic. This is often preferred for more complex scenarios, as it keeps validation logic separate from your model.

Step 1: Create the Validator Class #

public class PdfBlockValidator : IValidate<YourBlockTypeName>
{
    public IEnumerable<ValidationError> Validate(YourBlockTypeName instance)
    {
        // Check if the PDF button is enabled and the text is empty
        if (instance.DisplayPdfButton && string.IsNullOrWhiteSpace(instance.DownloadPdfText))
        {
            yield return new ValidationError
            {
                PropertyName = nameof(YourBlockTypeName.DownloadPdfText),
                ErrorMessage = "Download Pdf Text is required when Display PDF Button is checked.",
                Severity = ValidationErrorSeverity.Error
            };
        }
    }
}

Make sure to replace YourBlockTypeName with the actual name of your Block Type.

Step 2: Register the Validator #

EPiServer will automatically discover this validator if it's in a scanned assembly. If not, you can register it via dependency injection:

services.AddTransient<IValidate<YourBlockTypeName>, PdfBlockValidator>();

Bonus: Client-Side Validation #

For a better editor experience, add client-side validation to enforce the rule immediately when the checkbox is toggled. Add this script to your Block's edit view:

$(document).ready(function() {
    const displayCheckbox = $('#DisplayPdfButton');
    const downloadTextInput = $('#DownloadPdfText');

    function updateRequiredState() {
        if (displayCheckbox.is(':checked')) {
            downloadTextInput.attr('required', 'required');
        } else {
            downloadTextInput.removeAttr('required');
            // Clear any existing validation errors for this field
            downloadTextInput.removeClass('input-validation-error');
            $('#DownloadPdfText-error').remove();
        }
    }

    // Set initial state on page load
    updateRequiredState();

    // Update state when checkbox is toggled
    displayCheckbox.change(updateRequiredState);
});

Both approaches will ensure that DownloadPdfText is only required when DisplayPdfButton is set to true. Choose the one that fits best with your project's structure!

内容的提问来源于stack exchange，提问作者Ayo Adesina