Begins an asynchronous read from the stream that complete when at least one byte is read. This operation reads at most count bytes.

Syntax

Visual Basic (Declaration)
Public Overloads Overrides Function BeginRead( _ ByVal buffer() As Byte, _ ByVal offset As Integer, _ ByVal count As Integer, _ ByVal callback As AsyncCallback, _ ByVal state As Object _ ) As IAsyncResult

Visual Basic (Declaration)

Public Overloads Overrides Function BeginRead( _
   ByVal buffer() As Byte, _
   ByVal offset As Integer, _
   ByVal count As Integer, _
   ByVal callback As AsyncCallback, _
   ByVal state As Object _
) As IAsyncResult

Visual Basic (Usage)	Copy Code
Dim instance As SegmentedStream Dim buffer() As Byte Dim offset As Integer Dim count As Integer Dim callback As AsyncCallback Dim state As Object Dim value As IAsyncResult value = instance.BeginRead(buffer, offset, count, callback, state)

Visual Basic (Usage)

Copy Code

Dim instance As SegmentedStream
Dim buffer() As Byte
Dim offset As Integer
Dim count As Integer
Dim callback As AsyncCallback
Dim state As Object
Dim value As IAsyncResult
 
value = instance.BeginRead(buffer, offset, count, callback, state)

C#
public override IAsyncResult BeginRead( byte[] buffer, int offset, int count, AsyncCallback callback, object state )

Managed Extensions for C++
public: IAsyncResult* BeginRead( byte[]* buffer, int offset, int count, AsyncCallback* callback, Object* state ) override

C++/CLI
public: IAsyncResult^ BeginRead( array<byte>^ buffer, int offset, int count, AsyncCallback^ callback, Object^ state ) override

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 maximum number of bytes to read.
callback: The AsyncCallback delegate to be called when the operation is complete.
state: An object containing state information for this operation.

Return Value

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

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#	Copy Code
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)); }

Copy Code

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));
}

Remarks

This is the standard method to use when reading a stream asynchronously. If a fixed-length record buffer is being read, use the overloaded Read() method that includes the 'bool fill' parameter. If a variable-length record segment is being read, use the overloaded Read() method that includes the 'byte[] delimiter' parameter.

Requirements

Target Platforms: Microsoft .NET Framework 2.0