Dns.BeginGetHostAddresses Method

Asynchronously returns the Internet Protocol (IP) addresses for the specified host.

Namespace: System.Net
Assembly: System (in system.dll)

Public Shared Function BeginGetHostAddresses ( _
	hostNameOrAddress As String, _
	requestCallback As AsyncCallback, _
	state As Object _
) As IAsyncResult
Dim hostNameOrAddress As String
Dim requestCallback As AsyncCallback
Dim state As Object
Dim returnValue As IAsyncResult

returnValue = Dns.BeginGetHostAddresses(hostNameOrAddress, requestCallback, state)
public static IAsyncResult BeginGetHostAddresses (
	String hostNameOrAddress, 
	AsyncCallback requestCallback, 
	Object state
public static function BeginGetHostAddresses (
	hostNameOrAddress : String, 
	requestCallback : AsyncCallback, 
	state : Object
) : IAsyncResult
Not applicable.



The host name or IP address to resolve.


An AsyncCallback delegate that references the method to invoke when the operation is complete.


A user-defined object that contains information about the operation. This object is passed to the requestCallback delegate when the operation is complete.

Return Value

An IAsyncResult instance that references the asynchronous request.

Exception typeCondition


hostNameOrAddress is a null reference (Nothing in Visual Basic).


The length of hostNameOrAddress is greater than 126 characters.


An error is encountered when resolving hostNameOrAddress.


hostNameOrAddress is an invalid IP address.

The BeginGetHostAddresses method asynchronously queries a DNS server for the IP addresses that are associated with a host name. If hostNameOrAddress is an IP address, this address is returned without querying the DNS server.


This member emits trace information when you enable network tracing in your application. For more information, see Network Tracing.

When an empty string is passed as the host name, this method returns the IPv4 addresses of the local host for all operating systems except Windows Server 2003; for Windows Server 2003, both IPv4 and IPv6 addresses for the local host are returned.

The asynchronous BeginGetHostAddresses operation must be completed by calling the EndGetHostAddresses method. Typically, the method is invoked by the requestCallback delegate.

This method does not block until the operation is complete. To block until the operation is complete, use the GetHostAddresses method.

For more information about using the asynchronous programming model, see Calling Synchronous Methods Asynchronously

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0