webwindowconfigurator/Test.UI/Components/Layout/MainLayout.razor.cs

namespace Test.UI.Components.Layout
{
    public partial class MainLayout
    {
        protected string sideClass { get; set; } = "sidebar";

        protected void UpdateNavDisplay()
        {
            navLarge = !navLarge;
            sideClass = navLarge ? "sidebar" : "sidebarSmall";
        }

        private bool navLarge = true;
    }
}