Builds a public URL when IIS is behind a load balancer

ToPublicUrl.cs

public static string ToPublicUrl(this UrlHelper urlHelper, Uri relativeUri)
{
	var httpContext = urlHelper.RequestContext.HttpContext;

	var uriBuilder = new UriBuilder
	{
		Host = httpContext.Request.Url.Host,
		Path = "/",
		Port = 80,
		Scheme = "http",
	};

	if (httpContext.Request.IsLocal)
	{
		uriBuilder.Port = httpContext.Request.Url.Port;
	}

	return new Uri(uriBuilder.Uri, relativeUri).AbsoluteUri;
}