Dns.BeginGetHostEntry 方法

参考

定义

命名空间:: System.Net

程序集:: System.Net.NameResolution.dll

程序集:: System.dll

程序集:: netstandard.dll

重要

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将主机名或 IP 地址异步解析为 IPHostEntry 实例。

重载

BeginGetHostEntry(IPAddress, AsyncCallback, Object)	将 IP 地址异步解析为 IPHostEntry 实例。
BeginGetHostEntry(String, AsyncCallback, Object)	将主机名或 IP 地址异步解析为 IPHostEntry 实例。

BeginGetHostEntry(IPAddress, AsyncCallback, Object)

Source:: Dns.cs

Source:: Dns.cs

Source:: Dns.cs

将 IP 地址异步解析为 IPHostEntry 实例。

public:
 static IAsyncResult ^ BeginGetHostEntry(System::Net::IPAddress ^ address, AsyncCallback ^ requestCallback, System::Object ^ stateObject);

public static IAsyncResult BeginGetHostEntry (System.Net.IPAddress address, AsyncCallback? requestCallback, object? stateObject);

public static IAsyncResult BeginGetHostEntry (System.Net.IPAddress address, AsyncCallback requestCallback, object stateObject);

static member BeginGetHostEntry : System.Net.IPAddress * AsyncCallback * obj -> IAsyncResult

Public Shared Function BeginGetHostEntry (address As IPAddress, requestCallback As AsyncCallback, stateObject As Object) As IAsyncResult

参数

address: IPAddress

要解析的 IP 地址。

requestCallback: AsyncCallback

一个 AsyncCallback 委托，它引用操作完成时要调用的方法。

stateObject: Object

一个用户定义对象，其中包含操作的相关信息。当操作完成时，此对象会被传递给 requestCallback 委托。

IAsyncResult

引用异步请求的 IAsyncResult 实例。

例外

ArgumentNullException

address 为 null。

SocketException

解析 address 时遇到错误。

ArgumentException

address 是无效的 IP 地址。

示例

下面的代码示例使用 BeginGetHostEntry 方法将 IP 地址解析为 IPHostEntry 实例。

    // Signals when the resolve has finished.
public:
    static ManualResetEvent^ GetHostEntryFinished =
        gcnew ManualResetEvent(false);

    // define the state object for the callback. 
    // use hostName to correlate calls with the proper result.
    ref class ResolveState
    {
    public:
        String^ hostName;
        IPHostEntry^ resolvedIPs;

        ResolveState(String^ host)
        {
            hostName = host;
        }

        property IPHostEntry^ IPs 
        {
            IPHostEntry^ get()
            {
                return resolvedIPs;
            }

            void set(IPHostEntry^ IPs)
            {
                resolvedIPs = IPs;
            }
        }

        property String^ host 
        {
            String^ get()
            {
                return hostName;
            }

            void set(String^ host)
            {
                hostName = host;
            }
        }
    };

    // Record the IPs in the state object for later use.
    static void GetHostEntryCallback(IAsyncResult^ ar)
    {
        ResolveState^ ioContext = (ResolveState^)(ar->AsyncState);

        ioContext->IPs = Dns::EndGetHostEntry(ar);
        GetHostEntryFinished->Set();
    }


    // Determine the Internet Protocol(IP) addresses for this 
    // host asynchronously.
public:
    static void DoGetHostEntryAsync(String^ hostName)
    {
        GetHostEntryFinished->Reset();
        ResolveState^ ioContext = gcnew ResolveState(hostName);

        Dns::BeginGetHostEntry(ioContext->host,
            gcnew AsyncCallback(GetHostEntryCallback), ioContext);
        // Wait here until the resolve completes 
        // (the callback calls .Set())
        GetHostEntryFinished->WaitOne();

        Console::WriteLine("EndGetHostEntry({0}) returns:", ioContext->host);
      
        for (int i = 0; i < ioContext->IPs->AddressList->Length; i++)
        {
            Console::WriteLine("    {0}", ioContext->IPs->AddressList[i]->ToString());
        }

//      for each (IPAddress^ address in ioContext->IPs)
//      {
//          Console::WriteLine("{0} ", address);
//      }
    }

// Signals when the resolve has finished.
public static ManualResetEvent GetHostEntryFinished =
    new ManualResetEvent(false);

// Define the state object for the callback.
// Use hostName to correlate calls with the proper result.
public class ResolveState
{
    string hostName;
    IPHostEntry resolvedIPs;

    public ResolveState(string host)
    {
        hostName = host;
    }

    public IPHostEntry IPs
    {
        get { return resolvedIPs; }
        set { resolvedIPs = value; }
    }

    public string host
    {
        get { return hostName; }
        set { hostName = value; }
    }
}

// Record the IPs in the state object for later use.
public static void GetHostEntryCallback(IAsyncResult ar)
{
    ResolveState ioContext = (ResolveState)ar.AsyncState;
    ioContext.IPs = Dns.EndGetHostEntry(ar);
    GetHostEntryFinished.Set();
}

// Determine the Internet Protocol (IP) addresses for
// this host asynchronously.
public static void DoGetHostEntryAsync(string hostname)
{
    GetHostEntryFinished.Reset();
    ResolveState ioContext= new ResolveState(hostname);

    Dns.BeginGetHostEntry(ioContext.host,
        new AsyncCallback(GetHostEntryCallback), ioContext);

    // Wait here until the resolve completes (the callback
    // calls .Set())
    GetHostEntryFinished.WaitOne();

    Console.WriteLine("EndGetHostEntry({0}) returns:", ioContext.host);

    foreach (IPAddress address in ioContext.IPs.AddressList)
    {
        Console.WriteLine($"    {address}");
    }
}

' Signals when the resolve has finished.
Dim Shared GetHostEntryFinished As ManualResetEvent = New ManualResetEvent(False)

' Define the state object for the callback. 
' Use hostName to correlate calls with the proper result.
Class ResolveState
    
    Dim hostName As String
    Dim resolvedIPs As IPHostEntry

    Public Sub New(host As String)
        hostName = host
    End Sub

    Public Property IPs AS IPHostEntry
        Get
            Return resolvedIPs
        End Get
        Set
            resolvedIPs = value
        End Set
    End Property

    Public Property host As String
        Get
            Return hostName
        End Get
        Set
            hostName = value
        End Set
    End Property

End Class

' Record the IPs in the state object for later use.
Shared Sub GetHostEntryCallback(ar As IAsyncResult)

    Dim ioContext As ResolveState = ar.AsyncState

    ioContext.IPs = Dns.EndGetHostEntry(ar)
    GetHostEntryFinished.Set()

End Sub

' Determine the Internet Protocol (IP) addresses for 
' this host asynchronously.
Shared Sub DoGetHostEntryAsync(hostname As String)
    
    GetHostEntryFinished.Reset()
    Dim ioContext As ResolveState = New ResolveState(hostname)

    Dns.BeginGetHostEntry(ioContext.host,AddressOf GetHostEntryCallback, ioContext)

    ' Wait here until the resolve completes (the callback 
    ' calls .Set())
    GetHostEntryFinished.WaitOne()

    Console.WriteLine($"EndGetHostEntry({ioContext.host}) returns:")

    Dim addresses As IPAddress() = ioContext.IPs.AddressList

    Dim index As Integer
    For index = 0 To addresses.Length - 1
        Console.WriteLine($"    {addresses(index)}")
    Next index

End Sub

注解

方法 BeginGetHostEntry 异步查询 DNS 服务器，以获取与 IP 地址关联的 IP 地址和别名。

注意在应用程序中启用网络跟踪时，此成员会发出跟踪信息。有关详细信息，请参阅.NET Framework中的网络跟踪。

BeginGetHostEntry异步操作必须通过调用 EndGetHostEntry 方法来完成。通常，委托会调用 requestCallback 方法。

在操作完成之前，此方法不会阻止。若要在操作完成之前阻止，请使用 GetHostEntry 方法。

有关使用异步编程模型的详细信息，请参阅异步调用同步方法

适用于

BeginGetHostEntry(String, AsyncCallback, Object)

Source:: Dns.cs

Source:: Dns.cs

Source:: Dns.cs

将主机名或 IP 地址异步解析为 IPHostEntry 实例。

public:
 static IAsyncResult ^ BeginGetHostEntry(System::String ^ hostNameOrAddress, AsyncCallback ^ requestCallback, System::Object ^ stateObject);

public static IAsyncResult BeginGetHostEntry (string hostNameOrAddress, AsyncCallback? requestCallback, object? stateObject);

public static IAsyncResult BeginGetHostEntry (string hostNameOrAddress, AsyncCallback requestCallback, object stateObject);

static member BeginGetHostEntry : string * AsyncCallback * obj -> IAsyncResult

Public Shared Function BeginGetHostEntry (hostNameOrAddress As String, requestCallback As AsyncCallback, stateObject As Object) As IAsyncResult

参数

hostNameOrAddress: String

要解析的主机名或 IP 地址。

requestCallback: AsyncCallback

一个 AsyncCallback 委托，它引用操作完成时要调用的方法。

stateObject: Object

一个用户定义对象，其中包含操作的相关信息。当操作完成时，此对象会被传递给 requestCallback 委托。

IAsyncResult

引用异步请求的 IAsyncResult 实例。

例外

ArgumentNullException

hostNameOrAddress 为 null。

ArgumentOutOfRangeException

hostNameOrAddress 的长度超过 255 个字符。

SocketException

解析 hostNameOrAddress 时遇到错误。

ArgumentException

hostNameOrAddress 是无效的 IP 地址。

示例