How can Blazor applications reliably back up and restore form validation state?

Confirmed facts

Blazor keeps validation messages in an EditContext's ValidationMessageStore. The store exposes GetValidationMessages(FieldIdentifier), Add, Remove, and Clear methods. These APIs are the only reliable way to read or modify validation state.

Likely explanation

To back up validation state you must enumerate the fields you care about, collect their current messages into a serializable structure (e.g., Dictionary<FieldIdentifier, List<string>>), serialize that structure (JSON works), and store it where needed. Restoration reverses the process: deserialize, clear the existing store, re‑add each message list, then call EditContext.NotifyValidationStateChanged() so the UI updates.

Steps needed

1. Obtain the EditContext (via @ref on EditForm or a cascading parameter).
2. Implement BackupValidationState():
   • Create a Dictionary<FieldIdentifier, List<string>>.
   • For each FieldIdentifier you want to preserve, call editContext.GetValidationMessages(id) and add the list to the dictionary.
   • Serialize the dictionary with System.Text.Json.JsonSerializer (provide a custom converter for FieldIdentifier or store a tuple of (object, string) instead).
   • Persist the serialized string.
3. Implement RestoreValidationState():
   • Read the persisted string and deserialize it back to the dictionary.
   • Call validationMessageStore.Clear().
   • For each entry, invoke validationMessageStore.Add(id, messages).
   • Finally, call editContext.NotifyValidationStateChanged().
4. Decide where to keep the serialized string:
   • If validation state only needs to survive the current component instance (e.g., temporary UI reset), a private field in the component is sufficient.
   • If it must survive disposals, page navigations, or refreshes, store it in a scoped service (DI‑injected) or in browser sessionStorage/localStorage via JS interop.

Missing diagnostic detail

Do you need the validation state to persist across component disposals and page navigations? Your answer determines whether a scoped service or browser storage is required, or whether a simple component‑level field will suffice.