非同期操作のステータスのポーリングPolling for the Status of an Asynchronous Operation

非同期操作の結果の待機中に、他の作業を実行できるアプリケーションは、操作が完了するまで待機をブロックする必要はありません。Applications that can do other work while waiting for the results of an asynchronous operation should not block waiting until the operation completes. 次のオプションのいずれかを使用して、非同期操作が完了するまでの待機中に、手順の実行を継続します。Use one of the following options to continue executing instructions while waiting for an asynchronous operation to complete:

Example

次のコード例は、ユーザー指定のコンピューターのドメイン ネーム システム情報を取得するために、Dns クラスの非同期メソッドを使用してデモを実行します。The following code example demonstrates using asynchronous methods in the Dns class to retrieve Domain Name System information for a user-specified computer. この例では、非同期操作が開始され、操作が完了するまでコンソールにピリオド (".") が出力されます。This example starts the asynchronous operation and then prints periods (".") at the console until the operation is complete. この方法を使用する場合はこれらの引数は必要ないため、null (Visual Basic の場合は Nothing) は、BeginGetHostByNameAsyncCallbackObject パラメーターに渡されることに注意してください。Note that null (Nothing in Visual Basic) is passed for the BeginGetHostByNameAsyncCallback and Object parameters because these arguments are not required when using this approach.

/*
The following example demonstrates using asynchronous methods to
get Domain Name System information for the specified host computer.
This example polls to detect the end of the asynchronous operation.
*/

using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace Examples.AdvancedProgramming.AsynchronousOperations
{
    public class PollUntilOperationCompletes
    {
        static void UpdateUserInterface()
        {
            // Print a period to indicate that the application
            // is still working on the request.
            Console.Write(".");
        }
        public static void Main(string[] args)
        {
            // Make sure the caller supplied a host name.
            if (args.Length == 0 || args[0].Length == 0)
            {
                // Print a message and exit.
                Console.WriteLine("You must specify the name of a host computer.");
                return;
            }
            // Start the asychronous request for DNS information.
            IAsyncResult result = Dns.BeginGetHostEntry(args[0], null, null);
            Console.WriteLine("Processing request for information...");
            
            // Poll for completion information.
            // Print periods (".") until the operation completes.
            while (result.IsCompleted != true)
            {
                UpdateUserInterface();
            }
            // The operation is complete. Process the results.
            // Print a new line.
            Console.WriteLine();
            try 
            {
                IPHostEntry host = Dns.EndGetHostEntry(result);
                string[] aliases = host.Aliases;
                IPAddress[] addresses = host.AddressList;
                if (aliases.Length > 0)
                {
                    Console.WriteLine("Aliases");
                    for (int i = 0; i < aliases.Length; i++)
                    {
                        Console.WriteLine("{0}", aliases[i]);
                    }
                }
                if (addresses.Length > 0)
                {
                    Console.WriteLine("Addresses");
                    for (int i = 0; i < addresses.Length; i++)
                    {
                        Console.WriteLine("{0}",addresses[i].ToString());
                    }
                }
            }
            catch (SocketException e)
            {
                Console.WriteLine("An exception occurred while processing the request: {0}", e.Message);
            }
        }
    }
}

'The following example demonstrates using asynchronous methods to
'get Domain Name System information for the specified host computer.
'This example polls to detect the end of the asynchronous operation.

Imports System.Net
Imports System.Net.Sockets
Imports System.Threading

Namespace Examples.AdvancedProgramming.AsynchronousOperations

    Public Class PollUntilOperationCompletes
        Shared Sub UpdateUserInterface()
            ' Print a period to indicate that the application
            ' is still working on the request.
            Console.Write(".")
        End Sub
        Public Shared Sub Main(args() as String)
            ' Make sure the caller supplied a host name.
            If(args.Length = 0)
                ' Print a message and exit.
                Console.WriteLine("You must specify the name of a host computer.")
                End
            End If
            ' Start the asynchronous request for DNS information.
            Dim result as IAsyncResult= Dns.BeginGetHostEntry(args(0), Nothing, Nothing)
            Console.WriteLine("Processing request for information...")
            
            ' Poll for completion information.
            ' Print periods (".") until the operation completes.
            Do while result.IsCompleted <> True
                UpdateUserInterface()
            Loop
            ' The operation is complete. Process the results.
            ' Print a new line.
            Console.WriteLine()
            Try 
                Dim host as IPHostEntry = Dns.EndGetHostEntry(result)
                Dim  aliases() as String = host.Aliases
                Dim addresses() as IPAddress = host.AddressList
                Dim i as Integer
                If aliases.Length > 0
                    Console.WriteLine("Aliases")
                    For i = 0 To aliases.Length -1 
                        Console.WriteLine("{0}", aliases(i))
                    Next i
                End If
                If addresses.Length > 0
                    Console.WriteLine("Addresses")
                    For i = 0 To addresses.Length -1
                        Console.WriteLine("{0}", addresses(i).ToString())
                    Next i
                End If
            Catch e as SocketException
                  Console.WriteLine("An exception occurred while processing the request: {0}", e.Message)
            End Try
        End Sub
    End Class
End Namespace

関連項目See also