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TransmitFileOptions Enumeration

The TransmitFileOptions enumeration defines values used in file transfer requests.

This enumeration has a FlagsAttribute attribute that allows a bitwise combination of its member values.

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

<FlagsAttribute> _
Public Enumeration TransmitFileOptions

Member nameDescription
UseDefaultWorkerThreadUse the default thread to process long file transfer requests.
DisconnectStart a transport-level disconnect after all the file data has been queued for transmission. When used with ReuseSocket, these flags return the socket to a disconnected, reusable state after the file has been transmitted.
ReuseSocketThe socket handle may be reused when the request completes. This flag is valid only if Disconnect is also specified. When used with Disconnect, these flags return the socket to a disconnected, reusable state after the file has been transmitted.
WriteBehindComplete the file transfer request immediately, without pending. If this flag is specified and the file transfer succeeds, the data has been accepted by the system but not necessarily acknowledged by the remote end. Do not use this flag with the Disconnect and ReuseSocket flags.
UseSystemThreadUse system threads to process long file transfer requests.
UseKernelApcUse kernel asynchronous procedure calls (APCs) instead of worker threads to process long file transfer requests. Long requests are defined as requests that require more than a single read from the file or a cache; the request therefore depends on the size of the file and the specified length of the send packet.

Note   The flags Disconnect and ReuseSocket return the socket to a disconnected, reusable state after the file has been transmitted. These flags should not be used on a socket where quality of service (QOS) has been requested, because the service provider might immediately delete any quality of service associated with the socket before the file transfer has completed. The best approach for a QOS-enabled socket is to call Close when the file transfer has completed, rather than relying on these flags.

The following example demonstrates the use of TransmitFileOptions in a call to SendFile. The file "test.txt" is located in the root directory of the local machine. In this example, a prebuffer and postbuffer of data are created and sent to the remote host with the file. To use the system's default thread, UseDefaultWorkerThread is specified.

            ' Establish the local endpoint for the socket.
            Dim ipHost As IPHostEntry = Dns.GetHostEntry(Dns.GetHostName())
            Dim ipAddr As IPAddress = ipHost.AddressList(0)
            Dim ipEndPoint As New IPEndPoint(ipAddr, 11000)

            ' Create a TCP socket.
            Dim client As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)

            ' Connect the socket to the remote endpoint.

            ' Send file fileName to the remote host with preBuffer and postBuffer data.
            ' There is a text file test.txt located in the root directory.
            Dim fileName As String = "C:\test.txt"

            ' Create the preBuffer data.
            Dim string1 As String = String.Format("This is text data that precedes the file.{0}", Environment.NewLine)
            Dim preBuf() As Byte = Encoding.ASCII.GetBytes(string1)

            ' Create the postBuffer data.
            Dim string2 As String = String.Format("This is text data that will follow the file.{0}", Environment.NewLine)
            Dim postBuf() As Byte = Encoding.ASCII.GetBytes(string2)

            'Send file fileName with buffers and default flags to the remote device.
            Console.WriteLine("Sending {0} with buffers to the host.{1}", fileName, Environment.NewLine)
            client.SendFile(fileName, preBuf, postBuf, TransmitFileOptions.UseDefaultWorkerThread)

            ' Release the socket.

.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.