Stream.CopyToAsync Method (Stream)

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Asynchronously reads the bytes from the current stream and writes them to another stream.

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


Public Function CopyToAsync ( _
    destination As Stream _
) As Task
public Task CopyToAsync(
    Stream destination


  • destination
    Type: System.IO..::.Stream
    The stream to which the contents of the current stream will be copied.

Return Value

Type: System.Threading.Tasks..::.Task
A task that represents the asynchronous copy operation.


Exception Condition

destination is nullNothingnullptra null reference (Nothing in Visual Basic).


Either the current stream or the destination stream is disposed.


The current stream does not support reading, or the destination stream does not support writing.


The CopyToAsync method enables you to perform resource-intensive I/O operations without blocking the main thread. This performance consideration is particularly important in a Windows Windows Store app or desktop app where a time-consuming stream operation can block the UI thread and make your app appear as if it is not working. The async methods are used in conjunction with the async and await keywords in Visual Basic and C#.

Copying begins at the current position in the current stream.

Version Information

Windows Phone OS

Supported in: 8.1, 8.0

See Also


Stream Class

CopyToAsync Overload

System.IO Namespace