FtpWebRequest.BeginGetRequestStream(AsyncCallback, Object) 方法

定义

命名空间:

System.Net

程序集:

System.Net.Requests.dll

Source:

FtpWebRequest.cs

开始以异步方式打开请求的内容流以便写入。

public:
 override IAsyncResult ^ BeginGetRequestStream(AsyncCallback ^ callback, System::Object ^ state);

public override IAsyncResult BeginGetRequestStream (AsyncCallback? callback, object? state);

override this.BeginGetRequestStream : AsyncCallback * obj -> IAsyncResult

Public Overrides Function BeginGetRequestStream (callback As AsyncCallback, state As Object) As IAsyncResult

参数

callback

AsyncCallback

一个 AsyncCallback 委托，它引用操作完成时要调用的方法。

state

Object

一个用户定义对象，其中包含操作的相关信息。 操作完成时，此对象传递给 callback 委托。

返回

IAsyncResult

IAsyncResult 实例，指示操作的状态。

例外

InvalidOperationException

此前对此方法或 GetRequestStream() 的调用尚未完成。

WebException

未能建立到 FTP 服务器的连接。

ProtocolViolationException

Method 属性没有设置为 UploadFile。

示例

下面的代码示例演示如何启动异步操作以获取请求的流。 此代码示例是为类概述提供的更大示例的 FtpWebRequest 一部分。

// Command line arguments are two strings:
// 1. The url that is the name of the file being uploaded to the server.
// 2. The name of the file on the local machine.
//
static void Main()
{
   array<String^>^args = Environment::GetCommandLineArgs();

   // Create a Uri instance with the specified URI string.
   // If the URI is not correctly formed, the Uri constructor
   // will throw an exception.
   ManualResetEvent^ waitObject;
   Uri^ target = gcnew Uri( args[ 1 ] );
   String^ fileName = args[ 2 ];
   FtpState^ state = gcnew FtpState;
   FtpWebRequest ^ request = dynamic_cast<FtpWebRequest^>(WebRequest::Create( target ));
   request->Method = WebRequestMethods::Ftp::UploadFile;

   // This example uses anonymous logon.
   // The request is anonymous by default; the credential does not have to be specified. 
   // The example specifies the credential only to
   // control how actions are logged on the server.
   request->Credentials = gcnew NetworkCredential( "anonymous","janeDoe@contoso.com" );

   // Store the request in the object that we pass into the
   // asynchronous operations.
   state->Request = request;
   state->FileName = fileName;

   // Get the event to wait on.
   waitObject = state->OperationComplete;

   // Asynchronously get the stream for the file contents.
   request->BeginGetRequestStream( gcnew AsyncCallback( EndGetStreamCallback ), state );

   // Block the current thread until all operations are complete.
   waitObject->WaitOne();

   // The operations either completed or threw an exception.
   if ( state->OperationException != nullptr )
   {
      throw state->OperationException;
   }
   else
   {
      Console::WriteLine( "The operation completed - {0}", state->StatusDescription );
   }
}

// Command line arguments are two strings:
// 1. The url that is the name of the file being uploaded to the server.
// 2. The name of the file on the local machine.
//
public static void Main(string[] args)
{
    // Create a Uri instance with the specified URI string.
    // If the URI is not correctly formed, the Uri constructor
    // will throw an exception.
    ManualResetEvent waitObject;

    Uri target = new Uri (args[0]);
    string fileName = args[1];
    FtpState state = new FtpState();
    FtpWebRequest request = (FtpWebRequest)WebRequest.Create(target);
    request.Method = WebRequestMethods.Ftp.UploadFile;

    // This example uses anonymous logon.
    // The request is anonymous by default; the credential does not have to be specified.
    // The example specifies the credential only to
    // control how actions are logged on the server.

    request.Credentials = new NetworkCredential ("anonymous","janeDoe@contoso.com");

    // Store the request in the object that we pass into the
    // asynchronous operations.
    state.Request = request;
    state.FileName = fileName;

    // Get the event to wait on.
    waitObject = state.OperationComplete;

    // Asynchronously get the stream for the file contents.
    request.BeginGetRequestStream(
        new AsyncCallback (EndGetStreamCallback),
        state
    );

    // Block the current thread until all operations are complete.
    waitObject.WaitOne();

    // The operations either completed or threw an exception.
    if (state.OperationException != null)
    {
        throw state.OperationException;
    }
    else
    {
        Console.WriteLine("The operation completed - {0}", state.StatusDescription);
    }
}

注解

必须通过调用 EndGetRequestStream 方法完成异步操作。 通常， EndGetRequestStream 由 引用 callback的方法调用。 若要确定操作的状态，检查此方法返回的对象IAsyncResult中的属性。

此方法在等待流时不会阻止。 若要阻止，请调用 GetRequestStream 以代替此方法。

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。

备注

当你在应用程序中启用网络跟踪后，此成员将输出跟踪信息。 有关详细信息，请参阅.NET Framework中的网络跟踪。

调用方说明

此方法生成网络流量。

另请参阅

• FtpWebResponse
• FtpStatusCode
• WebRequestMethods.Ftp
• WebRequest
• WebResponse
• WebClient