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HttpWebRequest.KeepAlive 属性

  • 项目

获取或设置一个值，该值指示是否与 Internet 资源建立持久性连接。

**命名空间:**System.Net
**程序集:**System（在 system.dll 中）

语法

声明
Public Property KeepAlive As Boolean
用法
Dim instance As HttpWebRequest
Dim value As Boolean

value = instance.KeepAlive

instance.KeepAlive = value

public bool KeepAlive { get; set; }

public:
property bool KeepAlive {
    bool get ();
    void set (bool value);
}

/** @property */
public boolean get_KeepAlive ()

/** @property */
public void set_KeepAlive (boolean value)

public function get KeepAlive () : boolean

public function set KeepAlive (value : boolean)

属性值

如果对 Internet 资源的请求所包含的 Connection HTTP 标头带有 Keep-alive 这一值，则为 true；否则为 false。默认为 true。

备注

将此属性设置为 true 以发送带有 Keep-alive 值的 Connection HTTP 标头。应用程序使用 KeepAlive 指示持久连接的首选项。当 KeepAlive 属性为 true 时，应用程序与支持它们的服务器建立持久连接。

提示

使用 HTTP/1.1 时，Keep-Alive 默认情况下处于打开状态。将 KeepAlive 设置为 false 可能导致将 Connection: Close 标头发送到服务器。

示例

下面的代码示例将 KeepAlive 属性设置为 false 以避免与 Internet 资源建立持久性连接。

Imports System
Imports System.IO
Imports System.Net
Imports System.Text
Imports Microsoft.VisualBasic

using System;
using System.IO;
using System.Net;
using System.Text;

int main()
{
   try
   {
      
      // Create a new HttpWebRequest object.  Make sure that
      // a default proxy is set if you are behind a firewall.
      HttpWebRequest^ myHttpWebRequest1 = dynamic_cast<HttpWebRequest^>(WebRequest::Create( "https://www.contoso.com" ));
      myHttpWebRequest1->KeepAlive = false;
      
      // Assign the response object of HttpWebRequest to a HttpWebResponse variable.
      HttpWebResponse^ myHttpWebResponse1 = dynamic_cast<HttpWebResponse^>(myHttpWebRequest1->GetResponse());
      Console::WriteLine( "\nThe HTTP request Headers for the first request are: \n {0}", myHttpWebRequest1->Headers );
      Console::WriteLine( "Press Enter Key to Continue.........." );
      Console::Read();
      Stream^ streamResponse = myHttpWebResponse1->GetResponseStream();
      StreamReader^ streamRead = gcnew StreamReader( streamResponse );
      array<Char>^readBuff = gcnew array<Char>(256);
      int count = streamRead->Read( readBuff, 0, 256 );
      Console::WriteLine( "The contents of the Html page are.......\n" );
      while ( count > 0 )
      {
         String^ outputData = gcnew String( readBuff,0,count );
         Console::Write( outputData );
         count = streamRead->Read( readBuff, 0, 256 );
      }
      Console::WriteLine();
      
      // Close the Stream object.
      streamResponse->Close();
      streamRead->Close();
      
      // Release the resources held by response object.
      myHttpWebResponse1->Close();
      
      // Create a new HttpWebRequest object for the specified Uri.
      HttpWebRequest^ myHttpWebRequest2 = dynamic_cast<HttpWebRequest^>(WebRequest::Create( "https://www.contoso.com" ));
      myHttpWebRequest2->Connection = "Close";
      
      // Assign the response object of 'HttpWebRequest' to a 'HttpWebResponse' variable.
      HttpWebResponse^ myHttpWebResponse2 = dynamic_cast<HttpWebResponse^>(myHttpWebRequest2->GetResponse());
      
      // Release the resources held by response object.
      myHttpWebResponse2->Close();
      Console::WriteLine( "\nThe Http RequestHeaders are \n {0}", myHttpWebRequest2->Headers );
      
      Console::WriteLine( "\nPress 'Enter' Key to Continue........." );
      Console::Read();
   }
   catch ( ArgumentException^ e ) 
   {
      Console::WriteLine( "\nThe second HttpWebRequest Object* has raised an Argument Exception as 'Connection' Property is set to 'Close'" );
      Console::WriteLine( "\n {0}", e->Message );
   }
   catch ( WebException^ e ) 
   {
      Console::WriteLine( "WebException raised!" );
      Console::WriteLine( "\n {0}", e->Message );
      Console::WriteLine( "\n {0}", e->Status );
   }
   catch ( Exception^ e ) 
   {
      Console::WriteLine( "Exception raised!" );
      Console::WriteLine( "Source : {0} ", e->Source );
      Console::WriteLine( "Message : {0} ", e->Message );
   }

}

class HttpWebRequest_Connection
{
    public static void main(String[] args)
    {
        try {
            // Create a new HttpWebRequest object.Make sure that 
            // a default proxy is set if you are behind a fure wall.
            HttpWebRequest myHttpWebRequest1 = (HttpWebRequest)
                (WebRequest.Create("https://www.contoso.com"));
            myHttpWebRequest1.set_KeepAlive(false);

            // Assign the response object of HttpWebRequest to
            // a HttpWebResponse variable.
            HttpWebResponse myHttpWebResponse1 = (HttpWebResponse)
                (myHttpWebRequest1.GetResponse());

            Console.WriteLine("\nThe HTTP request Headers for the" 
                + " first request are: \n{0}", myHttpWebRequest1.get_Headers());
            Console.WriteLine("Press Enter Key to Continue..........");
            Console.Read();

            Stream streamResponse = myHttpWebResponse1.GetResponseStream();
            StreamReader streamRead = new StreamReader(streamResponse);
            char readBuff[] = new char[256];
            int count = streamRead.Read(readBuff, 0, 256);

            Console.WriteLine("The contents of the Html page are.......\n");
            while (count > 0) {
                String outputData = new String(readBuff, 0, count);
                Console.Write(outputData);
                count = streamRead.Read(readBuff, 0, 256);
            }
            Console.WriteLine();
            // Close the Stream object.
            streamResponse.Close();
            streamRead.Close();
            // Release the resources held by response object.
            myHttpWebResponse1.Close();
            // Create a new HttpWebRequest object for the specified Uri.
            HttpWebRequest myHttpWebRequest2 = (HttpWebRequest)
                (WebRequest.Create("https://www.contoso.com"));
            myHttpWebRequest2.set_Connection("Close");
            // Assign the response object of 'HttpWebRequest' to a 
            // 'HttpWebResponse' variable.
            HttpWebResponse myHttpWebResponse2 = (HttpWebResponse)
                (myHttpWebRequest2.GetResponse());
            // Release the resources held by response object.
            myHttpWebResponse2.Close();
            Console.WriteLine("\nThe Http RequestHeaders are \n{0}",
                myHttpWebRequest2.get_Headers());

            Console.WriteLine("\nPress 'Enter' Key to Continue.........");
            Console.Read();
        }
        catch (ArgumentException e) {
            Console.WriteLine("\nThe second HttpWebRequest object has"
                + " raised an Argument Exception as 'Connection' Property"
                + " is set to 'Close'");
            Console.WriteLine("\n{0}", e.get_Message());
        }
        catch (WebException e) {
            Console.WriteLine("WebException raised!");
            Console.WriteLine("\n{0}", e.get_Message());
            Console.WriteLine("\n{0}", e.get_Status());
        }
        catch (System.Exception e) {
            Console.WriteLine("Exception raised!");
            Console.WriteLine("Source :{0} ", e.get_Source());
            Console.WriteLine("Message :{0} ", e.get_Message());
        }
    } //main
} //HttpWebRequest_Connection

import System.*;
import System.IO.*;
import System.Net.*;
import System.Text.*;

class HttpWebRequest_Connection
{
    public static void main(String[] args)
    {
        try {
            // Create a new HttpWebRequest object.Make sure that 
            // a default proxy is set if you are behind a fure wall.
            HttpWebRequest myHttpWebRequest1 = (HttpWebRequest)
                (WebRequest.Create("https://www.contoso.com"));
            myHttpWebRequest1.set_KeepAlive(false);

            // Assign the response object of HttpWebRequest to
            // a HttpWebResponse variable.
            HttpWebResponse myHttpWebResponse1 = (HttpWebResponse)
                (myHttpWebRequest1.GetResponse());

            Console.WriteLine("\nThe HTTP request Headers for the" 
                + " first request are: \n{0}", myHttpWebRequest1.get_Headers());
            Console.WriteLine("Press Enter Key to Continue..........");
            Console.Read();

            Stream streamResponse = myHttpWebResponse1.GetResponseStream();
            StreamReader streamRead = new StreamReader(streamResponse);
            char readBuff[] = new char[256];
            int count = streamRead.Read(readBuff, 0, 256);

            Console.WriteLine("The contents of the Html page are.......\n");
            while (count > 0) {
                String outputData = new String(readBuff, 0, count);
                Console.Write(outputData);
                count = streamRead.Read(readBuff, 0, 256);
            }
            Console.WriteLine();
            // Close the Stream object.
            streamResponse.Close();
            streamRead.Close();
            // Release the resources held by response object.
            myHttpWebResponse1.Close();
            // Create a new HttpWebRequest object for the specified Uri.
            HttpWebRequest myHttpWebRequest2 = (HttpWebRequest)
                (WebRequest.Create("https://www.contoso.com"));
            myHttpWebRequest2.set_Connection("Close");
            // Assign the response object of 'HttpWebRequest' to a 
            // 'HttpWebResponse' variable.
            HttpWebResponse myHttpWebResponse2 = (HttpWebResponse)
                (myHttpWebRequest2.GetResponse());
            // Release the resources held by response object.
            myHttpWebResponse2.Close();
            Console.WriteLine("\nThe Http RequestHeaders are \n{0}",
                myHttpWebRequest2.get_Headers());

            Console.WriteLine("\nPress 'Enter' Key to Continue.........");
            Console.Read();
        }
        catch (ArgumentException e) {
            Console.WriteLine("\nThe second HttpWebRequest object has"
                + " raised an Argument Exception as 'Connection' Property"
                + " is set to 'Close'");
            Console.WriteLine("\n{0}", e.get_Message());
        }
        catch (WebException e) {
            Console.WriteLine("WebException raised!");
            Console.WriteLine("\n{0}", e.get_Message());
            Console.WriteLine("\n{0}", e.get_Status());
        }
        catch (System.Exception e) {
            Console.WriteLine("Exception raised!");
            Console.WriteLine("Source :{0} ", e.get_Source());
            Console.WriteLine("Message :{0} ", e.get_Message());
        }
    } //main
} //HttpWebRequest_Connection

平台

Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition

.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。

版本信息

.NET Framework

受以下版本支持：2.0、1.1、1.0

.NET Compact Framework

受以下版本支持：2.0、1.0

请参见

参考

HttpWebRequest 类
HttpWebRequest 成员
System.Net 命名空间