Dns.BeginResolve(String, AsyncCallback, Object) Metodo

Definizione

Spazio dei nomi:

System.Net

Assembly:

System.Net.NameResolution.dll

Origine:

Dns.cs

Attenzione

BeginResolve has been deprecated. Use BeginGetHostEntry instead.

Avvia una richiesta asincrona per risolvere un nome host DNS o un indirizzo IP in un'istanza di IPAddress.

public:
 static IAsyncResult ^ BeginResolve(System::String ^ hostName, AsyncCallback ^ requestCallback, System::Object ^ stateObject);

[System.Obsolete("BeginResolve has been deprecated. Use BeginGetHostEntry instead.")]
public static IAsyncResult BeginResolve (string hostName, AsyncCallback? requestCallback, object? stateObject);

[<System.Obsolete("BeginResolve has been deprecated. Use BeginGetHostEntry instead.")>]
static member BeginResolve : string * AsyncCallback * obj -> IAsyncResult

Public Shared Function BeginResolve (hostName As String, requestCallback As AsyncCallback, stateObject As Object) As IAsyncResult

Parametri

hostName

String

Nome DNS dell'host.

requestCallback

AsyncCallback

Delegato AsyncCallback cui fa riferimento il metodo da richiamare al completamento dell'operazione.

stateObject

Object

Oggetto definito dall'utente che contiene informazioni sull'operazione. Questo oggetto viene passato al delegato requestCallback al completamento dell'operazione.

Restituisce

IAsyncResult

Istanza di IAsyncResult che fa riferimento alla richiesta asincrona.

Attributi

ObsoleteAttribute

Eccezioni

ArgumentNullException

hostName è null.

SocketException

Il chiamante non dispone delle autorizzazioni per accedere alle informazioni DNS.

Esempio

Nell'esempio seguente viene usato BeginResolve per risolvere un nome host DNS in un oggetto IPAddress.

public ref class DnsBeginGetHostByName
{
public:
   static System::Threading::ManualResetEvent^ allDone = nullptr;
   ref class RequestState
   {
   public:
      IPHostEntry^ host;
      RequestState()
      {
         host = nullptr;
      }
   };

   static void RespCallback( IAsyncResult^ ar )
   {
      try
      {
         // Convert the IAsyncResult* Object* to a RequestState Object*.
         RequestState^ tempRequestState = dynamic_cast<RequestState^>(ar->AsyncState);
         
         // End the asynchronous request.
         tempRequestState->host = Dns::EndResolve( ar );
         allDone->Set();
      }
      catch ( ArgumentNullException^ e ) 
      {
         Console::WriteLine( "ArgumentNullException caught!!!" );
         Console::WriteLine( "Source : {0}", e->Source );
         Console::WriteLine( "Message : {0}", e->Message );
      }
      catch ( Exception^ e ) 
      {
         Console::WriteLine( "Exception caught!!!" );
         Console::WriteLine( "Source : {0}", e->Source );
         Console::WriteLine( "Message : {0}", e->Message );
      }
   }
};

int main()
{
   DnsBeginGetHostByName::allDone = gcnew ManualResetEvent( false );
   
   // Create an instance of the RequestState class.
   DnsBeginGetHostByName::RequestState^ myRequestState =
      gcnew DnsBeginGetHostByName::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",
      gcnew AsyncCallback( DnsBeginGetHostByName::RespCallback ), myRequestState );
   
   // Wait until asynchronous call completes.
   DnsBeginGetHostByName::allDone->WaitOne();
   Console::WriteLine( "Host name : {0}", myRequestState->host->HostName );
   Console::WriteLine( "\nIP address list : " );
   for ( int index = 0; index < myRequestState->host->AddressList->Length; index++ )
      Console::WriteLine( myRequestState->host->AddressList[ index ] );
   Console::WriteLine( "\nAliases : " );
   for ( int index = 0; index < myRequestState->host->Aliases->Length; index++ )
      Console::WriteLine( myRequestState->host->Aliases[ index ] );
}

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.
     allDone.WaitOne();
     Console.WriteLine("Host name : " + myRequestState.host.HostName);
     Console.WriteLine("\nIP address list : ");
     for(int index=0; index < myRequestState.host.AddressList.Length; index++)
     {
       Console.WriteLine(myRequestState.host.AddressList[index]);
     }
     Console.WriteLine("\nAliases : ");
     for(int index=0; index < myRequestState.host.Aliases.Length; index++)
     {
       Console.WriteLine(myRequestState.host.Aliases[index]);
     }
   }

   private static void RespCallback(IAsyncResult ar)
   {
     try
     {
       // Convert the IAsyncResult object to a RequestState object.
       RequestState tempRequestState = (RequestState)ar.AsyncState;
       // End the asynchronous request.
       tempRequestState.host = Dns.EndResolve(ar);
       allDone.Set();
     }
       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);
     }
   }
}

Class DnsBeginGetHostByName
    
    Class RequestState
        Public host As IPHostEntry
        
        Public Sub New()
            host = Nothing
        End Sub
    End Class
    
    
    Public Shared Sub Main()
     Try
        ' Create an instance of the RequestState class.
        Dim myRequestState As New RequestState()
        
        ' Begin an asynchronous request for information such as the host name, IP addresses, 
        ' or aliases for the specified URI.
        Dim asyncResult As IAsyncResult = CType(Dns.BeginResolve("www.contoso.com", AddressOf RespCallback, myRequestState),IAsyncResult)

        ' Wait until asynchronous call completes.
        While asyncResult.IsCompleted <> True
        End While
        
        Console.WriteLine(("Host name : " + myRequestState.host.HostName))
        Console.WriteLine(ControlChars.Cr + "IP address list : ")
        Dim index As Integer
        For index = 0 To myRequestState.host.AddressList.Length - 1
            Console.WriteLine(myRequestState.host.AddressList(index))
        Next index
        Console.WriteLine(ControlChars.Cr + "Aliases : ")

        For index = 0 To myRequestState.host.Aliases.Length - 1
            Console.WriteLine(myRequestState.host.Aliases(index))
        Next index
    catch e as Exception
            Console.WriteLine("Exception caught!!!")
            Console.WriteLine(("Source : " + e.Source))
            Console.WriteLine(("Message : " + e.Message))
    End Try
    End Sub
    
    
    Private Shared Sub RespCallback(ar As IAsyncResult)
        Try
            ' Convert the IAsyncResult object to a RequestState object.
            Dim tempRequestState As RequestState = CType(ar.AsyncState, RequestState)

            ' End the asynchronous request.
            tempRequestState.host = Dns.EndResolve(ar)
            Catch e As ArgumentNullException
            Console.WriteLine("ArgumentNullException caught!!!")
            Console.WriteLine(("Source : " + e.Source))
            Console.WriteLine(("Message : " + e.Message))
            Catch e As Exception
            Console.WriteLine("Exception caught!!!")
            Console.WriteLine(("Source : " + e.Source))
            Console.WriteLine(("Message : " + e.Message))
        End Try
    End Sub

Commenti

L'operazione asincrona BeginResolve deve essere completata chiamando il EndResolve metodo . In genere, il metodo viene richiamato dal requestCallback delegato.

Questo metodo non viene bloccato fino al completamento dell'operazione. Per bloccare fino al completamento dell'operazione, usare il Resolve metodo .

Per altre informazioni sull'uso del modello di programmazione asincrona, vedere Chiamata asincrona di metodi sincroni.

Nota

Questo membro genera informazioni di traccia quando si abilita la traccia di rete nell'applicazione. Per altre informazioni, vedere Traccia di rete in .NET Framework.

Vedi anche

• Panoramica della programmazione asincrona