using mshtml; 을 추가해야 한다.
이를 사용하기 위해서 참조 에서 Microsoft.mshtml 라이브러리를 추가한다.

internal string GetCurrentURL()
{
try
{
if (Explorer != null)
return (Explorer.Document as HTMLDocumentClass).url;
else
return string.Empty;
}
catch //(Exception Ex)
{
return string.Empty;
}
}


internal void SetCurrentUrl(string Url)
{
if (Url.Length > 2048)
// Show Error Message
else
(Explorer.Document as HTMLDocumentClass).url = Url;
}


internal void SetCurrentHTMLDoc(string NewHTMLDoc)
{
(Explorer.Document as HTMLDocumentClass).IHTMLDocument2_clear();
(Explorer.Document as HTMLDocumentClass).IHTMLDocument2_writeln(NewHTMLDoc);
(Explorer.Document as HTMLDocumentClass).IHTMLDocument2_close();
}

AND