Can't change error message for form validation

For a required field the validation you set is not fired. Since it is required, it has no sense to check for minimum length - the field cannot be empty and this is the first thing fired. So, I would try removing the required flag so the validation will get to your custom validation rule.

Thanks, Juraj. I did try that but that didn't seem to make a difference. I made one of the required fields not required and I put in the custom validation, but when I submitted the form only the required fields validated. I was able to submit the form and the text field with the minimum length of 1 remained blank.

If you want to check for empty value, use a regex. The minimum value validation is fired only if you enter something into the field. The validation is not fired for empty field. Try using minimum length 10 and type a shorter string. The custom validation message should be displayed.

Ah, thank you! Using a minimum length of 10 and typing in a shorter string worked and I saw my custom error message. But how would I check for an empty field using regex? I've tried using ^$ and ^\s*$ and neither were fired when I submitted the form.

Have you tried using ^(?!.*\S)
If this will not help, then the only other option would be a fully custom validation rule.

Thanks for your help.

Hi Juraj. I tried both of your suggestions but I didn't get anywhere. It looks like custom validations don't trigger for empty fields (as you've noted previously), and if you make the field required then you just get the standard message. Basically, I'm looking for a way to specify messages like "Please fill in the first name" and "Please check off one of the options above", etc. Is there no way to specify a different custom error message for each required field in a form?

How does your custom validation rule looks like? In the code you are checking the value - if null or empty, you can return false and this should fire the validation.

Here's what I have for the validate method in a class that inherits from ValidationRule<string>

    protected override bool Validate(string value)
    {
        return !string.IsNullOrWhiteSpace(value);
    }

But it never fires. The form submits without firing. If I make the field required, it gives me the default error message. I put breakpoints in the method and it only gets hit if I put at least one character in the field, but if I leave it blank then it doesn't fire.

When you debug the code - it there anything in the "value" variable? I think that if there is nothing filled out in the field -> there is nothing to validate so the validation is not fired.
One option would be to automatically fill the field with some hidden character and validate it against it + the value you want to have there, e.g. the length. Or, another option would be fully custom form component which will have the validation implemented in its code.

Thanks for those suggestions. What I tried was making a hidden field from component that had no value and then use the form builder's validation to compare the field I wanted to validate against the empty hidden field. While my custom message did show when I tried to submit without filling the field, the validation would keep firing even after I filled out the field. What am I missing?

What does the debug say - what code is hit and what are the values passed into the validation logic?