Forms and validation at scale – Blazor in depth (W8, lesson 4)

What you learn in this lesson

register a model with nested objects and collections with AddValidation and [ValidatableType] so that every level is validated

know the order of validation and put a rule for the whole file in the right place with IValidatableObject

edit the rows of a collection in static SSR and interactively, and explain the difference

build an asynchronous check with EditContext and ValidationMessageStore and discard stale answers

assign domain errors from the core to the right row with a path

announce errors and catch unsaved changes when the user leaves the page

A form with three fields almost validates itself. The Kladde's customer file has a contact, up to three addresses and up to ten contact persons, and it must be saved without an empty street in the second address going unnoticed. This lesson is about what is different with a form like that: where the rules live, who applies them in which order, what works in static SSR and what only works interactively, and what a check looks like that has to ask the server.

Where the Kladde stands

The lesson assumes K2: ContactForm with EditForm, FormName and [SupplyParameterFromForm] from 0605, the rule "edge or model" from 0408 and the error output for screen readers from 0613. New is the model CustomerRecord (the customer file) with the Contact, a list Addresses (1 to 3 entries) and a list ContactPersons (0 to 10). It lives in src/Kladde.Web/Customers/CustomerRecord.cs, and from here on it is one of the fixed facts of the case study. Keep your own names and carry the steps over. Questions of state across lost connections are covered by W8.1.2.

What you learn in this lesson

Where the Kladde stands

This lesson belongs to course W8