// Helpers for async GetHostByName, ResolveToAddresses, and Resolve - they're almost identical
// If hostName is an IPString and justReturnParsedIP==true then no reverse lookup will be attempted, but the original address is returned.
private static IAsyncResult HostResolutionBeginHelper(string hostName, bool justReturnParsedIp, bool throwOnIIPAny, AsyncCallback requestCallback, object state)
{
if (hostName == null)
{
throw new ArgumentNullException(nameof(hostName));
}
if (NetEventSource.IsEnabled)
{
NetEventSource.Info(null, hostName);
}
// See if it's an IP Address.
IPAddress ipAddress;
DnsResolveAsyncResult asyncResult;
if (IPAddress.TryParse(hostName, out ipAddress))
{
if (throwOnIIPAny && (ipAddress.Equals(IPAddress.Any) || ipAddress.Equals(IPAddress.IPv6Any)))
{
throw new ArgumentException(SR.net_invalid_ip_addr, nameof(hostName));
}
asyncResult = new DnsResolveAsyncResult(ipAddress, null, state, requestCallback);
if (justReturnParsedIp)
{
IPHostEntry hostEntry = NameResolutionUtilities.GetUnresolvedAnswer(ipAddress);
asyncResult.StartPostingAsyncOp(false);
asyncResult.InvokeCallback(hostEntry);
asyncResult.FinishPostingAsyncOp();
return(asyncResult);
}
}
else
{
asyncResult = new DnsResolveAsyncResult(hostName, null, state, requestCallback);
}
// Set up the context, possibly flow.
asyncResult.StartPostingAsyncOp(false);
// If the OS supports it and 'hostName' is not an IP Address, resolve the name asynchronously
// instead of calling the synchronous version in the ThreadPool.
if (NameResolutionPal.SupportsGetAddrInfoAsync && ipAddress == null)
{
ValidateHostName(hostName);
NameResolutionPal.GetAddrInfoAsync(asyncResult);
}
else
{
// Start the resolve.
Task.Factory.StartNew(
s => ResolveCallback(s),
asyncResult,
CancellationToken.None,
TaskCreationOptions.DenyChildAttach,
TaskScheduler.Default);
}
// Finish the flowing, maybe it completed? This does nothing if we didn't initiate the flowing above.
asyncResult.FinishPostingAsyncOp();
return(asyncResult);
}
