title: Add error message without using WithMessage() method in FluentValidation
body: <p>I have a question and would be grateful if anyone can help me.
  I am validating an object with &quot;FluentValidation&quot; in an ASP.NET project, and I would like to know if there is a way to add an error message in &quot;ValidationResult&quot; without using the WithMessage () method.
  I am needing to add an error message based on a condition that is not related to the properties of the validated class.
  I thank the attention.</p>