How to retrieve query string that starts with # instead of ? in .NET and save it into JSON

Question

I'm trying to receive the token which is one of the parameters send in a request that looks something like this:

https://myapp.com/myApp/oauthcallback#access_token=eyJhbGciOiJIUzUxMiJ9.eyJQQ&token_type=bearer&expires_in=120&state=

The problem is that the delimiters is # instead of ? and no matter that i do i cannot substract the parameters as they are not received in a request in my application.

[HttpGet]
[Route("~/oauthcallback")]
[AllowAnonymous]
public string Oauthcallback()
{      
    return HttpContext.Current.Request.Url.Query;
}

the method doesn't return anything, but if i change it to ? then it returns the query string. I need to do the same and make it a json but with # instead of ?