以結束非同步作業的方式封鎖應用程式執行
更新：2007 年 11 月
無法在等候非同步作業 (Asynchronous Operation) 結果時，繼續進行其他工作的應用程式，必須在作業完成之前維持封鎖。請使用下列其中一個選項，在等候非同步作業完成時，封鎖應用程式的主執行緒：
呼叫非同步作業的 EndOperationName 方法。此主題中會示範這個方法。
使用非同步作業的 BeginOperationName 方法所傳回之 IAsyncResult 的 AsyncWaitHandle 屬性。如需進行這個方法的範例，請參閱使用 AsyncWaitHandle 封鎖應用程式執行。
使用 EndOperationName 方法來封鎖 (直到非同步作業完成) 的應用程式，通常會先呼叫 BeginOperationName 方法，再執行不需要作業結果即可完成的所有工作，然後呼叫 EndOperationName。
範例
下列程式碼範例會示範使用 Dns 類別中的非同步方法，以擷取使用者指定之電腦的網域名稱系統資訊。請注意，null (在 Visual Basic 中為 Nothing) 會傳遞給 BeginGetHostByNamerequestCallback 和 stateObject 參數，因為在使用這個方法時，並不需要這些引數。
' The following example demonstrates using asynchronous methods to
' get Domain Name System information for the specified host computer.
Imports System
Imports System.Net
Imports System.Net.Sockets
Namespace Examples.AdvancedProgramming.AsynchronousOperations
Public Class BlockUntilOperationCompletes
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.
' This example does not use a delegate or user-supplied object
' so the last two arguments are Nothing.
Dim result as IAsyncResult = Dns.BeginGetHostEntry(args(0), Nothing, Nothing)
Console.WriteLine("Processing your request for information...")
' Do any additional work that can be done here.
Try
' EndGetHostByName blocks until the process completes.
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
/*
The following example demonstrates using asynchronous methods to
get Domain Name System information for the specified host computer.
*/
using System;
using System.Net;
using System.Net.Sockets;
namespace Examples.AdvancedProgramming.AsynchronousOperations
{
public class BlockUntilOperationCompletes
{
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 asynchronous request for DNS information.
// This example does not use a delegate or user-supplied object
// so the last two arguments are null.
IAsyncResult result = Dns.BeginGetHostEntry(args[0], null, null);
Console.WriteLine("Processing your request for information...");
// Do any additional work that can be done here.
try
{
// EndGetHostByName blocks until the process completes.
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);
}
}
}
}