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SslStream.BeginWrite Method

Begins an asynchronous write operation that writes Bytes from the specified buffer to the stream.

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

[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public override IAsyncResult BeginWrite(
	byte[] buffer,
	int offset,
	int count,
	AsyncCallback asyncCallback,
	Object asyncState


Type: System.Byte[]
A Byte array that supplies the bytes to be written to the stream.
Type: System.Int32
The zero-based location in buffer at which to begin reading bytes to be written to the stream.
Type: System.Int32
An Int32 value that specifies the number of bytes to read from buffer.
Type: System.AsyncCallback
An AsyncCallback delegate that references the method to invoke when the write operation is complete.
Type: System.Object
A user-defined object that contains information about the write operation. This object is passed to the asyncCallback delegate when the operation completes.

Return Value

Type: System.IAsyncResult
An IAsyncResult object indicating the status of the asynchronous operation.


buffer is null.


offset < 0.


offset > the length of buffer.


offset + count > the length of buffer.


The write operation failed.


There is already a write operation in progress.


This object has been closed.


Authentication has not occurred.


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 following code example demonstrates calling this method.

void ReadCallback(IAsyncResult ar)
    ClientState state = (ClientState) ar.AsyncState;
    SslStream stream =;
    // Read the  message sent by the client.
    // The end of the message is signaled using the
    // "<EOF>" marker.
    int byteCount = -1;
        Console.WriteLine("Reading data from the client.");
        byteCount = stream.EndRead(ar);
        // Use Decoder class to convert from bytes to UTF8
        // in case a character spans two buffers.
        Decoder decoder = Encoding.UTF8.GetDecoder();
        char[] chars = new char[decoder.GetCharCount(state.buffer,0, byteCount)];
        decoder.GetChars(state.buffer, 0, byteCount, chars,0);
        state.readData.Append (chars);
        // Check for EOF or an empty message.
        if (state.readData.ToString().IndexOf("<EOF>") == -1 && byteCount != 0)
            // We are not finished reading.
            // Asynchronously read more message data from  the client.
            stream.BeginRead(state.buffer, 0, state.buffer.Length, 
                new AsyncCallback(ReadCallback),
            Console.WriteLine("Message from the client: {0}", state.readData.ToString());

        // Encode a test message into a byte array.
        // Signal the end of the message using "<EOF>".
        byte[] message = Encoding.UTF8.GetBytes("Hello from the server.<EOF>");
        // Asynchronously send the message to the client.
        stream.BeginWrite(message, 0, message.Length, 
            new AsyncCallback(WriteCallback),
    catch (Exception readException)
        Console.WriteLine("Read error: {0}", readException.Message);

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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