You can split it up.
string sUrl = "http://www.abc.com/index.aspx";
string[] sDomain = sUrl.Split(new char[] {'/'});
foreach (string sOut in sDomain)
{
Response.Write(sOut + "<br />");
}
Of course, this will give you http:
www.abc.com index.aspx but you can ignore the http or you can keep it (in case of an https or ftp or whatever) and you can parse the strings back together.
string sRebuilt = sDomain[0] + @"//" + sDomain[2];
string sPage = sDomain[sDomain.Length-1];
Output will be:
http://www.abc.com
index.aspx