IsolatedStorageFileStream.BeginWrite Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Begins an asynchronous write.

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


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


  • buffer
    Type: array<System.Byte[]
    The buffer to write data to.
  • offset
    Type: System.Int32
    The byte offset in buffer at which to begin writing.
  • numBytes
    Type: System.Int32
    The maximum number of bytes to write.
  • userCallback
    Type: System.AsyncCallback
    The method to call when the asynchronous write operation is completed. This parameter is optional.
  • stateObject
    Type: System.Object
    The status of the asynchronous write.

Return Value

Type: System.IAsyncResult
An IAsyncResult that represents the asynchronous write, which is possibly still pending. This IAsyncResult must be passed to this stream's EndWrite method to ensure that the write is complete, then frees resources appropriately. This can be done either by the same code that called BeginWrite or in a callback passed to BeginWrite.


Exception Condition

The isolated store has been removed.


Isolated storage is disabled.


The buffer length minus offset is less than numBytes.


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


offset or numBytes is negative.


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


The stream has been disposed.


If a IsolatedStorageFileStream object 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.

You must call EndWrite with the IAsyncResult object that this method returns to find out how many bytes were written.

Version Notes

Silverlight for Windows Phone Silverlight for Windows Phone

 When this method is called within a Windows Phone application, the operation is executed synchronously. If you have to write a large amount of data and do not want to interrupt the UI thread, you can create a new thread and perform the operation on that thread.

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.