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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
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)
public IAsyncResult BeginGetResponse (
	AsyncCallback callback, 
	Object state
)
public override function BeginGetResponse (
	callback : AsyncCallback, 
	state : Object
) : IAsyncResult

Parameters

callback

The AsyncCallback delegate.

state

An object that contains state information for this request.

Return Value

An IAsyncResult that references the asynchronous request.

Exception typeCondition

InvalidOperationException

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

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 class RequestDeclare
{
    public FileWebRequest myFileWebRequest;

    public RequestDeclare()
    {
        myFileWebRequest = null;
    } //RequestDeclare
} //RequestDeclare

class FileWebRequestResBeginEnd
{
    public static ManualResetEvent allDone = new ManualResetEvent(false);

    public static void main(String[] args)
    {
        if (args.length < 1) {
            Console.WriteLine("\nPlease enter the file name as command line " 
                + " parameter:");
            Console.WriteLine("Usage:FileWebRequest_resbeginend <systemname>/" 
                + "<sharedfoldername>/<filename>\nExample:" 
            + "FileWebRequest_resbeginend shafeeque/shaf/hello.txt");
        }
        else {
            try {
                // Place a 'Webrequest'.
                WebRequest myWebRequest = WebRequest.Create("file://" 
                    + args[0]);

                // Create an instance of the 'RequestDeclare' and associating
                // the 'myWebRequest' to it.        
                RequestDeclare myRequestDeclare = new RequestDeclare();
                myRequestDeclare.myFileWebRequest = 
                    (FileWebRequest)(myWebRequest);

                // Begin the Asynchronous request for getting file content
                // using 'BeginGetResponse()' method.    
                IAsyncResult asyncResult = (IAsyncResult)(myRequestDeclare.
                    myFileWebRequest.BeginGetResponse(new AsyncCallback(
                    RespCallback), myRequestDeclare));
                allDone.WaitOne();
            }
            catch (ArgumentNullException e) {
                Console.WriteLine("ArgumentNullException is :" 
                    + e.get_Message());
            }
            catch (UriFormatException e) {
                Console.WriteLine("UriFormatException is :" 
                    + e.get_Message());
            }
        }
    } //main

    private static void RespCallback(IAsyncResult ar)
    {
        // State of request is asynchronous.
        RequestDeclare requestDeclare = (RequestDeclare)(ar.
            get_AsyncState());
        FileWebRequest myFileWebRequest = requestDeclare.myFileWebRequest;

        // End the Asynchronus request by calling the
        // 'EndGetResponse()' method.
        FileWebResponse myFileWebResponse = (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("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("File reading is over.");
    } //RespCallback
} //FileWebRequestResBeginEnd 

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

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

.NET Framework

Supported in: 2.0, 1.1, 1.0

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