private HashSet <RazorDiagnostic> Validate() { HashSet <RazorDiagnostic> diagnostics = null; if (string.IsNullOrWhiteSpace(Name)) { var diagnostic = RazorDiagnosticFactory.CreateTagHelper_InvalidRestrictedChildNullOrWhitespace(_parent.GetDisplayName()); diagnostics ??= new(); diagnostics.Add(diagnostic); } else if (Name != TagHelperMatchingConventions.ElementCatchAllName) { foreach (var character in Name) { if (char.IsWhiteSpace(character) || HtmlConventions.IsInvalidNonWhitespaceHtmlCharacters(character)) { var diagnostic = RazorDiagnosticFactory.CreateTagHelper_InvalidRestrictedChild(_parent.GetDisplayName(), Name, character); diagnostics ??= new(); diagnostics.Add(diagnostic); } } } return(diagnostics); }