BeginRead(Byte[],Int32,Int32,Boolean,AsyncCallback,Object) Method

Begins an asynchronous read from the stream that completes when the provided buffer is completely full, the number of bytes requested is read, or end of stream is reached.

[Visual Basic]
Overloads Public Overridable Function BeginRead( _
   ByVal buffer() As Byte, _
   ByVal offset As Integer, _
   ByVal count As Integer, _
   ByVal fill As Boolean, _
   ByVal callback As AsyncCallback, _
   ByVal state As Object _
) As IAsyncResult

[C#]
public virtual IAsyncResult BeginRead( 
   byte[] buffer,
   int offset,
   int count,
   bool fill,
   AsyncCallback callback,
   object state
);

[C++]
public: virtual IAsyncResult* BeginRead( 
   byte[]* buffer,
   int offset,
   int count,
   bool fill,
   AsyncCallback* callback,
   Object* state
)

[C++/CLI]
public:
virtual IAsyncResult^ BeginRead( 
   bytearray<buffer>^ buffer,
   int offset,
   int count,
   bool fill,
   AsyncCallback^ callback,
   Object^ state
)

Parameters

buffer: The storage location for the received data.
offset: The zero-based position in the buffer at which to store the received data.
count: The exact number of bytes to read.
fill: Always true, use this version of BeginRead to completely fill the buffer
callback: The AsyncCallback delegate to be called when the operation is complete.
state: An object containing state information for this operation.

Return Type

An IAsyncResult representing the asynchronous operation. To determine how many bytes were read, you must pass this IAsyncResult to the EndRead method of the stream. This should be done within your AsyncCallback event handler.

Exceptions

Exception	Description
IOException	Thrown when the stream is not Readable.
ArgumentNullException	Thrown when the buffer or callback is null.
ArgumentOutOfRangeException	Thrown when the offset is less than zero or when count is less than or equal to zero.
ArgumentException	Thrown when the (offset + count) > (buffer.Length).

Remarks

The purpose of this method is to provide a convenient way to read a fixed-length record from the stream. The EndRead method should be called when your AsyncCallback delegate is raised.

Example

The following example demonstrates asynchronously reading from the server using the stream interface. This involves creating a callback method in which the response is handled. If you would like to use fully asynchronous methods with events already implemented, try the low-level interface (Tcp.BeginRead & Tcp.BeginWrite).

[C#]



private void AsynchronousReadTest()

{

  // Connect to the server

  tcp1.Connect("atropos", 13);



  // DAYTIME protocol (port 13) sends data and closes, receive data.

  // This demonstrates receiving data asynchronously using the stream interface.

           

  // data buffer is a global variable

  databuffer = new byte[tcp1.ReceiveBufferSize];



  // Begin the asynchronous Read operation.

  tcp1.Stream.BeginRead(databuffer, 0, tcp1.ReceiveBufferSize, new System.AsyncCallback(MyCallback), null);

}


private void MyCallback(System.IAsyncResult ar)

{

  // End pending asynchronous request.

  if(ar.IsCompleted)

     tcp1.Stream.EndRead(ar);



  // Write result

  Debug.WriteLine(System.Text.Encoding.Default.GetString(databuffer));

}

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows ME, Windows 2000, Windows XP, Windows Server 2003, Windows Vista

See Also

Requirements

Language

BeginRead(Byte[],Int32,Int32,Boolean,AsyncCallback,Object) Method

Parameters

Return Type

Exceptions

Remarks

Example

Requirements

See Also