FileWebRequest.BeginGetResponse Method (AsyncCallback, Object)

 

Begins an asynchronous request for a file system resource.

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

[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public override IAsyncResult BeginGetResponse(
	AsyncCallback callback,
	object 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.

Exception Condition
InvalidOperationException

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

WebException

The FileWebRequest was aborted.

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 FileWebRequest myFileWebRequest;	

		public RequestDeclare()
	{
		myFileWebRequest = null;
	}
}


class FileWebRequest_resbeginend
{

	public static ManualResetEvent allDone = new ManualResetEvent(false);

	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.Message);
		   }
		   catch(UriFormatException e)
	      {
		      Console.WriteLine("UriFormatException is :"+e.Message);
	      }
	   }
	}

  private static void RespCallback(IAsyncResult ar)
  {	


		   // State of request is asynchronous.
			RequestDeclare requestDeclare=(RequestDeclare) ar.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.");	
	}

}

.NET Framework
Available since 1.1
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