Can you access the metadata of other properties for ASP.NET Core 2.1 MVC client side validation?

Question

I am looking at implementing some pretty simple client side validation by implementing the IClientModelValidator interface. Specifically I am creating a NotEqualTo (and later an EqualTo) validation attribute that will compare the value of one input to another.

To provide a nice UX I want to use the display name of both inputs in the error messages: "Password cannot be the same as Email" for example.

This is has obviously been done a million times and there are plenty of example around, but they are either for previous versions of MVC or are not using the display name of the other property.

Below is what I have so far. I have managed to grab the display name via the Display attribute in the server side IsValid(...) method, but I can't work out how to do similar for the client side AddValidation(...) method.

[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
public class NotEqualToAttribute : ValidationAttribute, IClientModelValidator
{
  private const string defaultErrorMessage = "{0} cannot be the same as {1}.";

  public string OtherProperty { get; private set; }

  public NotEqualToAttribute(string otherProperty) : base(defaultErrorMessage)
  {
    this.OtherProperty = otherProperty;
  }

  public override string FormatErrorMessage(string name) 
  {
    string.Format(base.ErrorMessageString, name, this.OtherProperty);
  }

  public void AddValidation(ClientModelValidationContext context)
  {
    context.Attributes.Add("data-val", "true");      
    context.Attributes.Add("data-val-notequalto", this.FormatErrorMessage(context.ModelMetadata.GetDisplayName());
    context.Attributes.Add("data-val-notequalto-otherproperty", this.otherProperty);
  }

  protected override ValidationResult IsValid(object value, ValidationContext validationContext)
  {
    if (value == null)
      return ValidationResult.Success;

    PropertyInfo otherProperty = validationContext.ObjectInstance.GetType().GetProperty(this.OtherProperty);
    object otherValue = otherProperty.GetValue(validationContext.ObjectInstance, null);

    if (!value.Equals(otherValue))
      return ValidationResult.Success;

    DisplayAttribute display = otherProperty.GetCustomAttribute<DisplayAttribute>();
    string otherName = display?.GetName() ?? this.OtherProperty;

    return new ValidationResult(string.Format(defaultErrorMessage, validationContext.DisplayName, otherName));
  }        
}

Answer 1

Typically I solved this myself after taking a break, just going to leave this here in case it helps someone else (or there is a better solution):

public void AddValidation(ClientModelValidationContext context)
{            
  context.Attributes.Add("data-val", "true");

  string otherName = 
    context.ModelMetadata.ContainerMetadata.Properties
      .Single(p => p.PropertyName == this.OtherProperty)
      .GetDisplayName();

  context.Attributes.Add("data-val-notequalto", 
    string.Format(defaultErrorMessage, context.ModelMetadata.GetDisplayName(), otherName)
  );
}

You can get to the meta data for the other properties via ClientModelValidationContext.ModelMetadata.ContainerMetadata.Properties