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MemoryStream.ReadAsync Method (Byte[], Int32, Int32, CancellationToken)

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

Asynchronously reads a sequence of bytes from the current stream, advances the position within the stream by the number of bytes read, and monitors cancellation requests.

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

public override Task<int> ReadAsync(
	byte[] buffer,
	int offset,
	int count,
	CancellationToken cancellationToken


Type: System.Byte []
The buffer to write the data into.
Type: System.Int32
The byte offset in buffer at which to begin writing data from the stream.
Type: System.Int32
The maximum number of bytes to read.
Type: System.Threading.CancellationToken
The token to monitor for cancellation requests. The default value is None.

Return Value

Type: System.Threading.Tasks.Task<Int32>
A task that represents the asynchronous read operation. The value of the TResult parameter contains the total number of bytes read into the buffer. The result value can be less than the number of bytes requested if the number of bytes currently available is less than the requested number, or it can be 0 (zero) if the end of the stream has been reached.


buffer is null.


offset or count is negative.


The sum of offset and count is larger than the buffer length.


The stream does not support reading.


The stream has been disposed.


The stream is currently in use by a previous read operation.

If the operation is canceled before it completes, the returned task contains the Canceled value for the Status property.

You can create a cancellation token by creating an instance of the CancellationTokenSource class and passing the Token property as the cancellationToken parameter.

Windows Phone OS

Supported in: 8.1, 8.0