Using FluentValidation's WithMessage method with parameters with a WarningMessage - fluentvalidation

Question

I am new at FluentValidation in general. I am writing a validator, and I can't seem to figure out how to do a .WithMessage with a WarningMessage instead of an ErrorMessage and use params.
I can do this:
RuleFor(x => x.Endorsement)
.Must((coverage, endorsement) => HaveCoveragePerAcreOverMinimum(_coverage, coverage))
.When(x => (!HaveSpecialRequest(_coverage) && !HavePermissionsToOverrideLimits()))
.WithMessage("Some error message {0}", x => x.MyError);
But that sets it as an ErrorMessage and I need a Warning Message. I tried this but no dice:
RuleFor(x => x.Endorsement)
.Must((coverage, endorsement) => HaveCoveragePerAcreOverMinimum(_coverage, coverage))
.When(x => (!HaveSpecialRequest(_coverage) && !HavePermissionsToOverrideLimits()))
.WithMessage(new WarningMessage("Some warning message {0}", x => x.MyError));

Answer 1

There's no direct implementation of Warning message in FluentValidation (or Mvc's ModelState).
In FluentValidation, you've got a
WithState() extension method that you can use for this purpose.
First, you can create an enum
public enum ValidationErrorLevel
{
Error,
Warning
}
Then, you can write a few extension methods, in a static class, to use warnings and errors.
One to use in your Validator classes
public static IRuleBuilderOptions<T, TProperty> AsWarning<T, TProperty>(this IRuleBuilderOptions<T, TProperty> rule)
{
return rule.WithState<T, TProperty>(x => ValidationErrorLevel.Warning);
}
You can use it this way
RuleFor(x => x.Endorsement)
.Must((coverage, endorsement) => HaveCoveragePerAcreOverMinimum(_coverage, coverage))
.When(x => (!HaveSpecialRequest(_coverage) && !HavePermissionsToOverrideLimits()))
.WithMessage("Some error message {0}", x => x.MyError)
.AsWarning();
Few other to use to manage your validation results
public static IList<ValidationFailure> GetWarnings(this ValidationResult result)
{
return result.Errors.Where(m => m.CustomState != null && Convert.ToInt32(m.CustomState) == (int)ValidationErrorLevel.Warning).ToList();
}
public static IList<ValidationFailure> GetErrors(this ValidationResult result)
{
return result.Errors.Except(result.GetWarnings()).ToList();
}
Then, you should use
validator.Validate(<someclass>)
instead of
validator.ValidateAndThrow(<someclass>)
var results = validator.Validate(<someclass>);
You can then put errors in ModelState, for example
foreach (var error in result.GetErrors()) {
ModelState.AddModelError(error.PropertyName, error.ErrorMessage);
}
and do something else for Warnings, for example put it in TempData
TempData["warnings"] = new List<string>();
((List<string>)TempData[WarningMessageKey]).AddRange(result.GetWarnings().Select(warning => warning.ErrorMessage));
Then you can display them like any other TempData.

Answer 2

Validation (in general) attaches errors to the ModelState - which in itself is an object so if you put a break point on the if(ModelState.IsValid) line you can look at the other properties of the ModelState.
The thing with errors (and error messages) they are either there or not. If there is no issue there is no error message and if there is an issue an error message will be added.
If I were you, if the model state is not valid in your controller I would get all error messages using
var allErrors = ModelState.Values.SelectMany(v => v.Errors);
and then iterate over each one and decide what you want to do with it.
I hope this answers or at least helps as I am not totally sure what you are asking / trying to get to.