FileStream.BeginRead Method

Begins an asynchronous read.

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


<SecuritySafeCriticalAttribute> _
Public Overrides Function BeginRead ( _
    array As Byte(), _
    offset As Integer, _
    numBytes As Integer, _
    userCallback As AsyncCallback, _
    stateObject As Object _
) As IAsyncResult
public override IAsyncResult BeginRead(
    byte[] array,
    int offset,
    int numBytes,
    AsyncCallback userCallback,
    Object stateObject


  • array
    Type: array<System.Byte[]
    The buffer to read data into.
  • offset
    Type: System.Int32
    The byte offset in array at which to begin reading.
  • numBytes
    Type: System.Int32
    The maximum number of bytes to read.
  • userCallback
    Type: System.AsyncCallback
    The method to be called when the asynchronous read operation is completed.
  • stateObject
    Type: System.Object
    A user-provided object that distinguishes this particular asynchronous read request from other requests.

Return Value

Type: System.IAsyncResult
An IAsyncResult that references the asynchronous read.


Exception Condition

The array length minus offset is less than numBytes.


array is nulla null reference (Nothing in Visual Basic).


offset or numBytes is negative.


An asynchronous read was attempted past the end of the file.

Version Information


Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0


For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.