I am new to Razor Pages. I have just one page, I have Index.cshtml and Index.cshtml.cs with

`public class IndexModel : PageModel`

There is also `_Layout.cshtml`.

I need to get username from `HttpContext Header.` and show username in `_Layout.cshtml` (there is navigation bar).

But I do not get where is the best place to put this code in Razor Pages?
I cannot put it into `Index.cshtml.cs OnGet`, because I need in Layout, at least I think so.

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This is outside this question, but FYI I use Azure Easy Auth and from documentation (and also other non Razor Pages projects) I see that `HttpContext.Request.Headers["X-MS-CLIENT-PRINCIPAL-ID"]` would contain Name I need.