Get host domain from URL?

You can use Request object or Uri object to get host of url.

Using Request.Url

string host = Request.Url.Host;

Using Uri

Uri myUri = new Uri("http://www.contoso.com:8080/");   
string host = myUri.Host;  // host is "www.contoso.com"

Try like this;

Uri.GetLeftPart( UriPartial.Authority )

Defines the parts of a URI for the Uri.GetLeftPart method.

http://www.contoso.com/index.htm?date=today --> http://www.contoso.com

http://www.contoso.com/index.htm#main --> http://www.contoso.com

nntp://news.contoso.com/[email protected] --> nntp://news.contoso.com

file://server/filename.ext --> file://server

Uri uriAddress = new Uri("http://www.contoso.com/index.htm#search");
Console.WriteLine("The path of this Uri is {0}", uriAddress.GetLeftPart(UriPartial.Authority));

Demo

Use Uri class and use Host property

Uri url = new Uri(@"http://support.domain.com/default.aspx?id=12345");
Console.WriteLine(url.Host);