Dns.BeginResolve(String, AsyncCallback, Object) Method
Definition
Important
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Caution
BeginResolve is obsoleted for this type, please use BeginGetHostEntry instead. https://go.microsoft.com/fwlink/?linkid=14202
Caution
BeginResolve has been deprecated. Use BeginGetHostEntry instead.
Caution
BeginResolve is obsoleted for this type, please use BeginGetHostEntry instead. http://go.microsoft.com/fwlink/?linkid=14202
Begins an asynchronous request to resolve a DNS host name or IP address to an IPAddress instance.
public:
static IAsyncResult ^ BeginResolve(System::String ^ hostName, AsyncCallback ^ requestCallback, System::Object ^ stateObject);
[System.Obsolete("BeginResolve is obsoleted for this type, please use BeginGetHostEntry instead. https://go.microsoft.com/fwlink/?linkid=14202")]
public static IAsyncResult BeginResolve (string hostName, AsyncCallback? requestCallback, object? stateObject);
[System.Obsolete("BeginResolve has been deprecated. Use BeginGetHostEntry instead.")]
public static IAsyncResult BeginResolve (string hostName, AsyncCallback? requestCallback, object? stateObject);
[System.Obsolete("BeginResolve is obsoleted for this type, please use BeginGetHostEntry instead. http://go.microsoft.com/fwlink/?linkid=14202")]
public static IAsyncResult BeginResolve (string hostName, AsyncCallback requestCallback, object stateObject);
[System.Obsolete("BeginResolve is obsoleted for this type, please use BeginGetHostEntry instead. https://go.microsoft.com/fwlink/?linkid=14202")]
public static IAsyncResult BeginResolve (string hostName, AsyncCallback requestCallback, object stateObject);
public static IAsyncResult BeginResolve (string hostName, AsyncCallback requestCallback, object stateObject);
[<System.Obsolete("BeginResolve is obsoleted for this type, please use BeginGetHostEntry instead. https://go.microsoft.com/fwlink/?linkid=14202")>]
static member BeginResolve : string * AsyncCallback * obj -> IAsyncResult
[<System.Obsolete("BeginResolve has been deprecated. Use BeginGetHostEntry instead.")>]
static member BeginResolve : string * AsyncCallback * obj -> IAsyncResult
[<System.Obsolete("BeginResolve is obsoleted for this type, please use BeginGetHostEntry instead. http://go.microsoft.com/fwlink/?linkid=14202")>]
static member BeginResolve : string * AsyncCallback * obj -> IAsyncResult
static member BeginResolve : string * AsyncCallback * obj -> IAsyncResult
Public Shared Function BeginResolve (hostName As String, requestCallback As AsyncCallback, stateObject As Object) As IAsyncResult
Parameters
- hostName
- String
The DNS name of the host.
- requestCallback
- AsyncCallback
An AsyncCallback delegate that references the method to invoke when the operation is complete.
- stateObject
- Object
A user-defined object that contains information about the operation. This object is passed to the requestCallback
delegate when the operation is complete.
Returns
An IAsyncResult instance that references the asynchronous request.
- Attributes
Exceptions
hostName
is null
.
The caller does not have permission to access DNS information.
Examples
The following example uses BeginResolve to resolve a DNS host name to an 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
Remarks
The asynchronous BeginResolve operation must be completed by calling the EndResolve 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 Resolve method.
For more information about using the asynchronous programming model, see Calling Synchronous Methods Asynchronously.
Note
This member emits trace information when you enable network tracing in your application. For more information, see Network Tracing in the .NET Framework.