SharePoint 2010 how to find the subsite name programaticlly and refer the Parent site WebPart

I have List created in the Parent Web and created a Visual WebPart to pull the data from the list and display. When I add the same WebPart in the SubSite pages the data is not populating to display. When I try the following condition:

String siteUrl = SPContext.Current.Web.ParentWeb.Url; //Featch the top site url

data is populating in the SubSites and not display in the Parent site.

How can I conditionally change the site url path for Parent site and Sub sites to refer the list created in Parent site.