FluentValidation rule for null object

Question

I\'ve been trying to work out how to create a FluentValidation rule that checks if the instance of an object it\'s validating is not null, prior to validating it\'s properti

Answer 1

Override EnsureInstanceNotNull as below

protected override void EnsureInstanceNotNull(object instanceToValidate)
{
    if(instanceToValidate==null)
      throw new ValidationException("Customer can not be null");
}

Answer 2

I can't really test that right now, but you can either try to override Validate, or include the rules in the When block:

public CustomerValidator()
{
     When(x => x != null, () => {
         RuleFor(x => x.Surname).NotEmpty();
         //etc.
     });
}

Answer 3

By means of Custom(). It can be also very helpful when validation of another field is based on validation of your current field.

ruleBuilder.Custom((obj, context) =>
        {
            if (obj != null)
            {
                var propertyName = <field where should be validation>;
                context.AddFailure(propertyName, "'Your field name' Your validation message.");
            }
        });