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FileWebRequest.BeginGetResponse Method

Begins an asynchronous request for a file system resource.

Namespace:  System.Net
Assembly:  System (in System.dll)

'Declaration
<HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading := True)> _
Public Overrides Function BeginGetResponse ( _
	callback As AsyncCallback, _
	state As Object _
) As IAsyncResult
'Usage
Dim instance As FileWebRequest 
Dim callback As AsyncCallback 
Dim state As Object 
Dim returnValue As IAsyncResult 

returnValue = instance.BeginGetResponse(callback, _
	state)

Parameters

callback
Type: System.AsyncCallback

The AsyncCallback delegate.

state
Type: System.Object

An object that contains state information for this request.

Return Value

Type: System.IAsyncResult
An IAsyncResult that references the asynchronous request.

ExceptionCondition
InvalidOperationException

The stream is already in use by a previous call to BeginGetResponse.

NoteNote:

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: ExternalThreading. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

The asynchronous callback method that implements the AsyncCallback delegate uses the EndGetResponse method to return the actual FileWebResponse.

The following code example uses the BeginGetResponse method to asynchronously access a file system resource.

Public Class RequestDeclare
    Public myFileWebRequest As FileWebRequest

    Public Sub New()
        myFileWebRequest = Nothing 
    End Sub ' New 
End Class ' RequestDeclare



Class FileWebRequest_resbeginend

    Public Shared allDone As New ManualResetEvent(False)

    ' Entry point which delegates to C-style main Private Function. 
    Public Overloads Shared Sub Main()
        Main(GetCommandLineArgs())
    End Sub 

    Overloads Shared Sub Main(args() As String)

        If args.Length < 2 Then
            Console.WriteLine(ControlChars.Cr + "Please enter the file name as command line parameter:")
            Console.WriteLine("Usage:FileWebRequest_resbeginend " + ChrW(60) + "systemname" + ChrW(62) + "/" + ChrW(60) + "sharedfoldername" + ChrW(62) + "/" + ChrW(60) + "filename" + ChrW(62) + ControlChars.Cr + "Example:FileWebRequest_resbeginend shafeeque/shaf/hello.txt")

        Else 
            Try 

                ' Place a webrequest. 
                Dim myWebRequest As WebRequest = WebRequest.Create(("file://" + args(1)))
                ' Create an instance of the 'RequestDeclare' and associating the 'myWebRequest' to it.		 
                Dim myRequestDeclare As New RequestDeclare()
                myRequestDeclare.myFileWebRequest = CType(myWebRequest, FileWebRequest)

                ' Begin the Asynchronous request for getting file content using 'BeginGetResponse()' method.	 
                 Dim asyncResult As IAsyncResult = CType(myRequestDeclare.myFileWebRequest.BeginGetResponse(AddressOf RespCallback, myRequestDeclare), IAsyncResult)
                 allDone.WaitOne()


            Catch e As ArgumentNullException
                Console.WriteLine(("ArgumentNullException is :" + e.Message))
            Catch e As UriFormatException
                Console.WriteLine(("UriFormatException is :" + e.Message))
            End Try 
        End If 
    End Sub ' Main


    Private Shared Sub RespCallback(ar As IAsyncResult)



        ' State of request is asynchronous. 
        Dim requestDeclare As RequestDeclare = CType(ar.AsyncState, RequestDeclare)

        Dim myFileWebRequest As FileWebRequest = requestDeclare.myFileWebRequest

        ' End the Asynchronus request by calling the 'EndGetResponse()' method. 
        Dim myFileWebResponse As FileWebResponse = CType(myFileWebRequest.EndGetResponse(ar), FileWebResponse)

        ' Reade the response into Stream. 
        Dim streamReader As New StreamReader(myFileWebResponse.GetResponseStream())


        Dim readBuffer(256) As [Char]

        Dim count As Integer = streamReader.Read(readBuffer, 0, 256)

        Console.WriteLine("The contents of the file are :"+ControlChars.Cr)

        While count > 0
            Dim str As New [String](readBuffer, 0, count)
            Console.WriteLine(str)
            count = streamReader.Read(readBuffer, 0, 256)
        End While
	     streamReader.Close()
        ' Release the response object resources.
	     myFileWebResponse.Close()
        allDone.Set()
        Console.WriteLine("File reading is over.")
    End Sub ' RespCallback 
End Class ' FileWebRequest_resbeginend
public __gc class RequestDeclare {
public:
   FileWebRequest*  myFileWebRequest;

   RequestDeclare() {
      myFileWebRequest = 0;
   }
};

__gc class FileWebRequest_resbeginend {
public:
   static ManualResetEvent* allDone = new ManualResetEvent(false);

   static void RespCallback(IAsyncResult* ar) {
      // State of request is asynchronous.
      RequestDeclare* requestDeclare = dynamic_cast<RequestDeclare*>(ar->AsyncState);

      FileWebRequest*  myFileWebRequest=requestDeclare->myFileWebRequest;

      // End the Asynchronus request by calling the 'EndGetResponse()' method.
      FileWebResponse* myFileWebResponse = dynamic_cast<FileWebResponse*> (myFileWebRequest->EndGetResponse(ar));

      // Reade the response into Stream.
      StreamReader* streamReader = new StreamReader(myFileWebResponse->GetResponseStream());

      Char readBuffer[] = new Char[256];
      int count = streamReader->Read(readBuffer, 0, 256);
      Console::WriteLine(S"The contents of the file are :\n");

      while (count > 0) {
         String* str = new String(readBuffer, 0, count);
         Console::WriteLine(str);
         count = streamReader->Read(readBuffer, 0, 256);
      }

      streamReader->Close();
      // Release the response Object* resources.
      myFileWebResponse->Close();
      allDone->Set();
      Console::WriteLine(S"File reading is over.");
   }
};

int main() {
   String* args[] = Environment::GetCommandLineArgs();
   if (args->Length < 2) {
      Console::WriteLine(S"\nPlease enter the file name as command line parameter:");
      Console::WriteLine(S"Usage:FileWebRequest_resbeginend <systemname>/<sharedfoldername>/<filename>\n");
      Console::WriteLine(S"Example:FileWebRequest_resbeginend shafeeque/shaf/hello.txt");
   } else {
      try {
         // Place a 'Webrequest'.
         WebRequest* myWebRequest= WebRequest::Create(String::Concat(S"file://", args[1]));
         // Create an instance of the 'RequestDeclare' and associating the 'myWebRequest' to it.
         RequestDeclare* myRequestDeclare = new RequestDeclare();
         myRequestDeclare->myFileWebRequest = dynamic_cast<FileWebRequest*>(myWebRequest);

         // Begin the Asynchronous request for getting file content using 'BeginGetResponse()' method.
         IAsyncResult* asyncResult = dynamic_cast<IAsyncResult*>
            (myRequestDeclare->myFileWebRequest->BeginGetResponse(new AsyncCallback(0, 
            &FileWebRequest_resbeginend::RespCallback), myRequestDeclare));
         FileWebRequest_resbeginend::allDone->WaitOne();
      } catch (ArgumentNullException* e) {
         Console::WriteLine(S"ArgumentNullException is : {0}", e->Message);
      } catch (UriFormatException* e) {
         Console::WriteLine(S"UriFormatException is : {0}", e->Message);
      }
   }
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
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