BeginWrite Method

DeflateStream.BeginWrite Method

Begins an asynchronous write operation.

Namespace:  System.IO.Compression
Assembly:  System (in System.dll)

[<HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)>]
abstract BeginWrite : 
        array:byte[] * 
        offset:int * 
        count:int * 
        asyncCallback:AsyncCallback * 
        asyncState:Object -> IAsyncResult 
[<HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)>]
override BeginWrite : 
        array:byte[] * 
        offset:int * 
        count:int * 
        asyncCallback:AsyncCallback * 
        asyncState:Object -> IAsyncResult 


Type: System.Byte[]
The buffer to write data from.
Type: System.Int32
The byte offset in buffer to begin writing from.
Type: System.Int32
The maximum number of bytes to write.
Type: System.AsyncCallback
An optional asynchronous callback, to be called when the write is complete.
Type: System.Object
A user-provided object that distinguishes this particular asynchronous write request from other requests.

Return Value

Type: System.IAsyncResult
An IAsyncResult object that represents the asynchronous write, which could still be pending.


An asynchronous write past the end of the stream was attempted, or a disk error occurred.


One or more of the arguments is invalid.


Methods were called after the stream was closed.


The current DeflateStream implementation does not support the write operation.


The write operation cannot be performed because the stream is closed.

Pass the IAsyncResult object returned by the current method to EndWrite to ensure that the write completes and frees resources appropriately. You can do this either by using the same code that called BeginWrite or in a callback passed to BeginWrite. If an error occurs during an asynchronous write, an exception will not be thrown until EndWrite is called with the IAsyncResult returned by this method.

If a stream is writable, writing at the end of the stream expands the stream.

The current position in the stream is updated when you issue the asynchronous read or write, not when the I/O operation completes. Multiple simultaneous asynchronous requests render the request completion order uncertain.

Use the CanWrite property to determine whether the current DeflateStream object supports writing.

If a stream is closed or you pass an invalid argument, exceptions are thrown immediately from BeginWrite. Errors that occur during an asynchronous write request, such as a disk failure during the I/O request, occur on the thread pool thread and throw exceptions when calling EndWrite.


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.

.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.

Community Additions

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