Blazor Server and Blazor WebAssembly support page layout. There are three ways to apply a layout to pages. (1) Specifying a layout explicitly for an individual page. (2) Specifying a default layout for all pages in an app. (3) Specifying the layout for all components in a folder and subfolders.
https://medium.com/informatics/blazor-server-project-5-924279f6fc7f