BufferedStream.ReadAsync Method
Definition
Important
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Overloads
| ReadAsync(Memory<Byte>, CancellationToken) |
Asynchronously reads a sequence of bytes from the current buffered stream and advances the position within the buffered stream by the number of bytes read. |
| ReadAsync(Byte[], Int32, Int32, CancellationToken) |
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. |
ReadAsync(Memory<Byte>, CancellationToken)
- Source:
- BufferedStream.cs
- Source:
- BufferedStream.cs
- Source:
- BufferedStream.cs
Asynchronously reads a sequence of bytes from the current buffered stream and advances the position within the buffered stream by the number of bytes read.
public override System.Threading.Tasks.ValueTask<int> ReadAsync (Memory<byte> buffer, System.Threading.CancellationToken cancellationToken = default);override this.ReadAsync : Memory<byte> * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<int>Public Overrides Function ReadAsync (buffer As Memory(Of Byte), Optional cancellationToken As CancellationToken = Nothing) As ValueTask(Of Integer)Parameters
- cancellationToken
- CancellationToken
The token to monitor for cancellation requests. The default value is None.
Returns
A task that represents the asynchronous read operation. The value of its Result property contains the total number of bytes read into the buffer. The result value can be less than the number of bytes allocated in the buffer if that many bytes are not currently available, or it can be 0 (zero) if the end of the stream has been reached.
Exceptions
The cancellation token was canceled. This exception is stored into the returned task.
Remarks
The ReadAsync method enables you to perform resource-intensive I/O operations without blocking the main thread. This performance consideration is particularly important in a Windows 8.x 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#.
Use the CanRead property to determine whether the current instance supports reading.
If the operation is canceled before it completes, the returned task contains the TaskStatus.Canceled value for the Status property.
Applies to
ReadAsync(Byte[], Int32, Int32, CancellationToken)
- Source:
- BufferedStream.cs
- Source:
- BufferedStream.cs
- Source:
- BufferedStream.cs
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.
public:
override System::Threading::Tasks::Task<int> ^ ReadAsync(cli::array <System::Byte> ^ buffer, int offset, int count, System::Threading::CancellationToken cancellationToken);public override System.Threading.Tasks.Task<int> ReadAsync (byte[] buffer, int offset, int count, System.Threading.CancellationToken cancellationToken);override this.ReadAsync : byte[] * int * int * System.Threading.CancellationToken -> System.Threading.Tasks.Task<int>Public Overrides Function ReadAsync (buffer As Byte(), offset As Integer, count As Integer, cancellationToken As CancellationToken) As Task(Of Integer)Parameters
- buffer
- Byte[]
The buffer to write the data into.
- offset
- Int32
The byte offset in buffer at which to begin writing data from the stream.
- count
- Int32
The maximum number of bytes to read.
- cancellationToken
- CancellationToken
The token to monitor for cancellation requests.
Returns
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.
Exceptions
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.
The cancellation token was canceled. This exception is stored into the returned task.
Remarks
You can create a cancellation token by creating an instance of the CancellationTokenSource class and passing the Token property as the cancellationToken parameter.
This method stores in the task it returns all non-usage exceptions that the method's synchronous counterpart can throw. If an exception is stored into the returned task, that exception will be thrown when the task is awaited. Usage exceptions, such as ArgumentException, are still thrown synchronously. For the stored exceptions, see the exceptions thrown by Read(Byte[], Int32, Int32).
