Dns.EndResolve Method (IAsyncResult)


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Note: This API is now obsolete.

Ends an asynchronous request for DNS information.

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

[ObsoleteAttribute("EndResolve is obsoleted for this type, please use EndGetHostEntry instead. http://go.microsoft.com/fwlink/?linkid=14202")]
public static IPHostEntry EndResolve(
	IAsyncResult asyncResult


Type: System.IAsyncResult

An IAsyncResult instance that is returned by a call to the BeginResolve method.

Return Value

Type: System.Net.IPHostEntry

An IPHostEntry object that contains DNS information about a host.

Exception Condition

asyncResult is null.

This method blocks until the operation is complete.

If the Ipv6Element.Enabled is set to true, the Aliases property of the IPHostEntry instance returned is not populated by this method and will always be empty.

To perform this operation synchronously, use the Resolve method.


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

The following example ends an asynchronous request for DNS host information.

class DnsBeginGetHostByName
   public static System.Threading.ManualResetEvent allDone = null;

   class RequestState
      public IPHostEntry host;
      public RequestState()
         host = null;

   public static void Main()
     allDone = new ManualResetEvent(false);
     // Create an instance of the RequestState class.
     RequestState myRequestState = new RequestState();

     // Begin an asynchronous request for information like host name, IP addresses, or 
     // aliases for specified the specified URI.
     IAsyncResult asyncResult = Dns.BeginResolve("www.contoso.com", new AsyncCallback(RespCallback), myRequestState );

     // Wait until asynchronous call completes.
     Console.WriteLine("Host name : " + myRequestState.host.HostName);
     Console.WriteLine("\nIP address list : ");
     for(int index=0; index < myRequestState.host.AddressList.Length; index++)
     Console.WriteLine("\nAliases : ");
     for(int index=0; index < myRequestState.host.Aliases.Length; index++)

   private static void RespCallback(IAsyncResult ar)
       // Convert the IAsyncResult object to a RequestState object.
       RequestState tempRequestState = (RequestState)ar.AsyncState;
       // End the asynchronous request.
       tempRequestState.host = Dns.EndResolve(ar);
	   catch(ArgumentNullException e) 
       Console.WriteLine("ArgumentNullException caught!!!");
       Console.WriteLine("Source : " + e.Source);
       Console.WriteLine("Message : " + e.Message);
     catch(Exception e)
       Console.WriteLine("Exception caught!!!");
       Console.WriteLine("Source : " + e.Source);
       Console.WriteLine("Message : " + e.Message);

.NET Framework
Available since 1.1
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