Solution: (I am almost certain this will help someone)
See this link for the source of this solution in VB (thanks jshardy!), all I did was convert to C#.
NB: You must be using ONLY basic authentication on IIS for this to work, but it can probably be adapted. You also need to pass a Page instance in, or at least the Request.ServerVariables property (or use 'this' if called from a Page code-behind directly). I'd tidy this up and probably remove the use of references but this is a faithful translation of the original solution and you can make any amendments necessary.
public static void ServiceCall(Page p)
{
LocalServices.ServiceName s = new LocalServices.ServiceName();
s.PreAuthenticate = true; /* Not sure if required */
string username = "";
string password = "";
string domain = "";
GetBasicCredentials(p, ref username, ref password, ref domain);
s.Credentials = new NetworkCredential(username, password, domain);
s.ServiceMethod();
}
/* Converted from: http://forums.asp.net/t/1172902.aspx */
private static void GetBasicCredentials(Page p, ref string rstrUser, ref string rstrPassword, ref string rstrDomain)
{
if (p == null)
{
return;
}
rstrUser = "";
rstrPassword = "";
rstrDomain = "";
rstrUser = p.Request.ServerVariables["AUTH_USER"];
rstrPassword = p.Request.ServerVariables["AUTH_PASSWORD"];
SplitDomainUserName(rstrUser, ref rstrDomain, ref rstrUser);
/* MSDN KB article 835388
BUG: The Request.ServerVariables("AUTH_PASSWORD") object does not display certain characters from an ASPX page */
string lstrHeader = p.Request.ServerVariables["HTTP_AUTHORIZATION"];
if (!string.IsNullOrEmpty(lstrHeader) && lstrHeader.StartsWith("Basic"))
{
string lstrTicket = lstrHeader.Substring(6);
lstrTicket = System.Text.Encoding.Default.GetString(Convert.FromBase64String(lstrTicket));
rstrPassword = lstrTicket.Substring((lstrTicket.IndexOf(":") + 1));
}
/* At least on my XP Pro machine AUTH_USER is not set (probably because we're using Forms authentication
But if the password is set (either by AUTH_PASSWORD or HTTP_AUTHORIZATION)
then we can use LOGON_USER*/
if (string.IsNullOrEmpty(rstrUser) && !string.IsNullOrEmpty(rstrPassword))
{
rstrUser = p.Request.ServerVariables["LOGON_USER"];
SplitDomainUserName(rstrUser, ref rstrDomain, ref rstrUser);
}
}
/* Converted from: http://forums.asp.net/t/1172902.aspx */
private static void SplitDomainUserName(string pstrDomainUserName, ref string rstrDomainName, ref string rstrUserName)
{
rstrDomainName = "";
rstrUserName = pstrDomainUserName;
int lnSlashPos = pstrDomainUserName.IndexOf("\\");
if (lnSlashPos > 0)
{
rstrDomainName = pstrDomainUserName.Substring(0, lnSlashPos);
rstrUserName = pstrDomainUserName.Substring(lnSlashPos + 1);
}
}