Dns.BeginGetHostEntry 方法

定义

命名空间:: System.Net

程序集:: netstandard.dll, System.Net.NameResolution.dll

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

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 =
    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

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

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 =
    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 在 DNS 服务器中查询与主机名或 IP 地址关联的 IP 地址。