CryptoStream.ReadAsync Method

Definition

Namespace:

System.Security.Cryptography

Assembly:

System.Security.Cryptography.dll

Overloads

ReadAsync(Byte[], Int32, Int32, CancellationToken)	Reads a sequence of bytes from the current stream asynchronously, advances the position within the stream by the number of bytes read, and monitors cancellation requests.
ReadAsync(Memory<Byte>, 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(Byte[], Int32, Int32, CancellationToken)

Source:

CryptoStream.cs

Reads a sequence of bytes from the current stream asynchronously, 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. The default value is None.

Returns

Task<Int32>

A task that represents the asynchronous read operation. The value of the task object's TResult parameter contains the total number of bytes read into the buffer. The result 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

ArgumentNullException

buffer is null.

ArgumentOutOfRangeException

offset or count is negative.

ArgumentException

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

NotSupportedException

The stream does not support reading.

ObjectDisposedException

The stream has been disposed.

InvalidOperationException

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

OperationCanceledException

The cancellation token was canceled. This exception is stored into the returned task.

Remarks

Important

Starting in .NET 6, this method might not read as many bytes as were requested. For more information, see Partial and zero-byte reads in DeflateStream, GZipStream, and CryptoStream.

You must preface your call to ReadAsync with the await (C#) or Await (Visual Basic) operator to suspend execution of the method until the task is complete. For more information, see Asynchronous programming (C#) or Asynchronous programming with Async and Await (Visual Basic).

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

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).

See also

• Cancellation in managed threads

ReadAsync(Memory<Byte>, CancellationToken)

Source:

CryptoStream.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.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

buffer

Memory<Byte>

The region of memory to write the data into.

cancellationToken

CancellationToken

The token to monitor for cancellation requests. The default value is None.

Returns

ValueTask<Int32>

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

NotSupportedException

The CryptoStreamMode associated with the current CryptoStream object does not match the underlying stream. For example, this exception is thrown when using Read with an underlying stream that's write only.

OperationCanceledException

The cancellation token was canceled. This exception is stored into the returned task.

Remarks

Starting in .NET 6, this method might not read as many bytes as were requested. For more information, see Partial and zero-byte reads in DeflateStream, GZipStream, and CryptoStream.