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.NET MAUI › Advanced Data Binding & Collections

How do you implement input validation with data binding?

Intermediate

Answer

Expose validation state on the view model (per-field error properties or INotifyDataErrorInfo), bind UI to show errors (DataTrigger or an error label), and disable submit via a command's CanExecute. The CommunityToolkit and behaviors package also offer validation behaviors for common rules.
public bool HasEmailError => string.IsNullOrEmpty(Email) ||
    !Email.Contains('@');
// Submit command CanExecute returns !HasEmailError && ...
Real-world example A signup form highlights invalid fields and keeps the Create button disabled until all validations pass.

Common follow-ups: What is INotifyDataErrorInfo? | How do you disable submit on errors?

Validation Data Binding & MVVM Advanced Data Binding & Collections
All 6 Advanced Data Binding & Collections questions