Resolve a Hostname to an IP Address

The System.Net namespace contains much of the functionality, including such basics as the IPAddress and Dns classes.

string host = "www.microsoft.com";
//note that a host can have multiple IP addresses
IPAddress[] addresses = Dns.GetHostAddresses(host);
foreach (IPAddress addr in addresses)
{
    Console.Write("\t{0}", addr);
}

Here is the output from a sample run of a few common hostnames:

www.microsoft.com
        207.46.19.254   207.46.19.190
www.live.com
        204.2.160.40    204.2.160.49
www.google.com
        208.67.219.230  208.67.219.231
www.yahoo.com
        209.131.36.158