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BufferedStream.BeginRead Method

.NET Framework 4.5

Begins an asynchronous read operation. (Consider using ReadAsync instead; see the Remarks section.)

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

public override IAsyncResult BeginRead(
	byte[] buffer,
	int offset,
	int count,
	AsyncCallback callback,
	Object state
)

Parameters

buffer
Type: System.Byte[]

The buffer to read the data into.

offset
Type: System.Int32

The byte offset in buffer at which to begin writing data read from the stream.

count
Type: System.Int32

The maximum number of bytes to read.

callback
Type: System.AsyncCallback

An optional asynchronous callback, to be called when the read is complete.

state
Type: System.Object

A user-provided object that distinguishes this particular asynchronous read request from other requests.

Return Value

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

ExceptionCondition
ArgumentNullException

buffer is null.

ArgumentOutOfRangeException

offset or count is negative.

IOException

Attempted an asynchronous read past the end of the stream.

ArgumentException

The buffer length minus offset is less than count.

NotSupportedException

The current stream does not support the read operation.

In the .NET Framework 4 and earlier versions, you have to use methods such as BeginRead and EndRead 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 for every call to BeginRead. Failing to end a read process before beginning another read can cause undesirable behavior such as deadlock.

NoteNote

Use the CanRead property to determine whether the current instance supports reading.

EndRead must be called with this IAsyncResult to find out how many bytes were read.

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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