protected internal FormValueRequiredAttribute(
     FormValueRequirementOperator requirement,
     FormValueRequirementMatch rule,
     bool inverse,
     params string[] submitButtonNames)
 {
     // At least one submit button should be found (or being absent if 'inverse')
     _submitButtonNames = submitButtonNames;
     _operator          = requirement;
     _match             = rule;
     _inverse           = inverse;
 }
 public FormValueRequiredAttribute(FormValueRequirementOperator requirement, FormValueRequirementMatch rule, params string[] submitButtonNames)
     : this(requirement, rule, false, submitButtonNames)
 {
 }
 public FormValueAbsentAttribute(FormValueRequirementOperator requirement, FormValueRequirementMatch rule, params string[] submitButtonNames)
     : base(requirement, rule, true, submitButtonNames)
 {
 }