Request root path (host path + virtual path)

HttpRequestMessageHelpers.cs

public static class HttpRequestMessageHelpers
{
    private const char separator = '/';

    public static string GetRootPath(this HttpRequestMessage message)
        => GetHostPath(message) + separator + GetVirtualPath(message);

    private static string GetHostPath(HttpRequestMessage message)
        => message.RequestUri.GetLeftPart(UriPartial.Authority).TrimEnd(separator);

    private static string GetVirtualPath(HttpRequestMessage message)
        => message.GetRequestContext().VirtualPathRoot.TrimStart(separator);
}