How can I get the root domain URI in ASP.NET?

string baseUrl = Request.Url.GetLeftPart(UriPartial.Authority);

Uri::GetLeftPart Method:

The GetLeftPart method returns a string containing the leftmost portion of the URI string, ending with the portion specified by part.

UriPartial Enumeration:

The scheme and authority segments of the URI.

For anyone still wondering, a more complete answer is available at http://devio.wordpress.com/2009/10/19/get-absolut-url-of-asp-net-application/.

public string FullyQualifiedApplicationPath{    get    {        //Return variable declaration        var appPath = string.Empty;        //Getting the current context of HTTP request        var context = HttpContext.Current;        //Checking the current context content        if (context != null)        {            //Formatting the fully qualified website url/name            appPath = string.Format("{0}://{1}{2}{3}",                                    context.Request.Url.Scheme,                                    context.Request.Url.Host,                                    context.Request.Url.Port == 80                                        ? string.Empty                                        : ":" + context.Request.Url.Port,                                    context.Request.ApplicationPath);        }        if (!appPath.EndsWith("/"))            appPath += "/";        return appPath;    }}

HttpContext.Current.Request.Url can get you all the info on the URL. And can break down the url into its fragments.