Conditional Form Validation
Environment
| Product | Form for Blazor |
Description
How to apply custom conditional validation, based on user selection?
How to implement conditional required validation for a form field? There are fields that I want to set as required only when another field has a certain value.
How to set dynamic validation for Blazor form fields? I want to update the validation criteria of a TextBox at runtime.
Solution
The TelerikForm supports any validator that is compatible with the Blazor EditForm and EditContext. There are several options to validate form values conditionally:
- Use a third-party validator that allows conditional validation.
- Perform custom validation in the Form's
OnSubmitevent. - Implement remote (server-side) custom validation.
- Use
FormItemTemplates. Subscribe to the change handlers of the field editors to execute custom logic, show notifications, etc. -
Implement a conditional
DataAnnotationattribute. To see inline error messages next to the field editor, use theValidationResultoverload that passes a field name. In this way the form validator will know which field has failed validation.return new ValidationResult(this.FormatErrorMessage(validationContext.DisplayName), new List<string> { validationContext.MemberName });