public IEnumerable <ValidationResult> ValidateCommands(IEnumerable <ICommand> commands)
 {
     foreach (var command in commands)
     {
         var validators = dispatcher.GetValidators(command);
         foreach (var validator in validators)
         {
             foreach (var validationResult in validator.Validate(command))
             {
                 yield return(validationResult);
             }
         }
     }
 }