BeginWrite Method

BufferedStream.BeginWrite Method (Byte[], Int32, Int32, AsyncCallback, Object)

.NET Framework 4.6 and 4.5

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

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

public override IAsyncResult BeginWrite(
	byte[] buffer,
	int offset,
	int count,
	AsyncCallback callback,
	object state


Type: System.Byte[]

The buffer containing data to write to the current stream.

Type: System.Int32

The zero-based byte offset in buffer at which to begin copying bytes to the current stream.

Type: System.Int32

The maximum number of bytes to write.

Type: System.AsyncCallback

The method to be called when the asynchronous write operation is completed.

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 references the asynchronous write which could still be pending.

Exception Condition

buffer length minus offset is less than count.


buffer is null.


offset or count is negative.


The stream does not support writing.

In the .NET Framework 4 and earlier versions, you have to use methods such as BeginWrite and EndWrite to implement asynchronous file operations. These methods are still available in the .NET Framework 4.5 to support legacy code; however, the new async methods, such as ReadAsync, WriteAsync, and FlushAsync, help you implement asynchronous file operations more easily.

EndWrite must be called exactly once on every IAsyncResult from BeginWrite. EndWrite will block until the I/O operation has completed.

.NET Framework
Available since 4.5
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