DeflateStream::BeginWrite Method (array<Byte>^, Int32, Int32, AsyncCallback^, Object^)


Begins an asynchronous write operation. (Consider using the Stream::WriteAsync method instead; see the Remarks section.)

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

[HostProtectionAttribute(SecurityAction::LinkDemand, ExternalThreading = true)]
virtual IAsyncResult^ BeginWrite(
	array<unsigned char>^ array,
	int offset,
	int count,
	AsyncCallback^ asyncCallback,
	Object^ asyncState
) override


Type: array<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 operation 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 object that represents the asynchronous write operation, which could still be pending.

Exception Condition

The method tried to write asynchronously past the end of the stream, 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.

Starting with the .NET Framework 4.5, you can perform asynchronous write operations by using the WriteAsync method. The BeginWrite method is still available in the .NET Framework 4.5 to support legacy code; however, you can implement asynchronous I/O operations more easily by using the new async methods. For more information, see .

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 operation, 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 operation, 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.

.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
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