// ReSharper disable CheckNamespace namespace Microsoft.AspNetCore.Mvc.Rendering; public static class HtmlHelpersExtensions { public static string IsActive(this IHtmlHelper html, string? page, string activeClass = "active") { if (string.IsNullOrEmpty(page)) { return string.Empty; } var actualPage = html.ViewContext.RouteData.Values.GetValueOrDefault("page")?.ToString(); if (string.IsNullOrEmpty(actualPage)) { return string.Empty; } return actualPage.StartsWith(page, StringComparison.OrdinalIgnoreCase) ? activeClass : string.Empty; } }