Getting the left section of current Url upto domain name in C#

I was creating product's full links dynamically to do this I need to have the left section of the current URL from http to end of domain name.

Example:

My full link:
http://pro-post.blogspot.in/2014/07/extended-dropdownlistfor-to-create.html

I need: 
http://pro-post.blogspot.in

To achieve this ->

string leftSection = System.Web.HttpContext.Current.Request.Url.OriginalString.Replace(
System.Web.HttpContext.Current.Request.Url.PathAndQuery, "")
leftSection = leftSection.Substring(0, leftSection.LastIndexOf(':'));

ref: Soumyadip [http://soumyadip-cooldips.blogspot.in]