StreamReader.ReadBlockAsync Method
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Overloads
| ReadBlockAsync(Memory<Char>, CancellationToken) |
Asynchronously reads the characters from the current stream and writes the data to a buffer. |
| ReadBlockAsync(Char[], Int32, Int32) |
Reads a specified maximum number of characters from the current stream asynchronously and writes the data to a buffer, beginning at the specified index. |
ReadBlockAsync(Memory<Char>, CancellationToken)
- Source:
- StreamReader.cs
- Source:
- StreamReader.cs
- Source:
- StreamReader.cs
Asynchronously reads the characters from the current stream and writes the data to a buffer.
public override System.Threading.Tasks.ValueTask<int> ReadBlockAsync (Memory<char> buffer, System.Threading.CancellationToken cancellationToken = default);override this.ReadBlockAsync : Memory<char> * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<int>Public Overrides Function ReadBlockAsync (buffer As Memory(Of Char), Optional cancellationToken As CancellationToken = Nothing) As ValueTask(Of Integer)Parameters
When this method returns, contains the specified memory block of characters replaced by the characters read from the current source.
- cancellationToken
- CancellationToken
The token to monitor for cancellation requests. The default value is None.
Returns
A value task that represents the asynchronous read operation. The value of the type parameter of the value task contains the total number of characters read into the buffer. The result value can be less than the number of characters requested if the number of characters currently available is less than the requested number, 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.
Applies to
ReadBlockAsync(Char[], Int32, Int32)
- Source:
- StreamReader.cs
- Source:
- StreamReader.cs
- Source:
- StreamReader.cs
Reads a specified maximum number of characters from the current stream asynchronously and writes the data to a buffer, beginning at the specified index.
public:
override System::Threading::Tasks::Task<int> ^ ReadBlockAsync(cli::array <char> ^ buffer, int index, int count);public override System.Threading.Tasks.Task<int> ReadBlockAsync (char[] buffer, int index, int count);[System.Runtime.InteropServices.ComVisible(false)]
public override System.Threading.Tasks.Task<int> ReadBlockAsync (char[] buffer, int index, int count);override this.ReadBlockAsync : char[] * int * int -> System.Threading.Tasks.Task<int>[<System.Runtime.InteropServices.ComVisible(false)>]
override this.ReadBlockAsync : char[] * int * int -> System.Threading.Tasks.Task<int>Public Overrides Function ReadBlockAsync (buffer As Char(), index As Integer, count As Integer) As Task(Of Integer)Parameters
- buffer
- Char[]
When this method returns, contains the specified character array with the values between index and (index + count - 1) replaced by the characters read from the current source.
- index
- Int32
The position in buffer at which to begin writing.
- count
- Int32
The maximum number of characters to read. If the end of the stream is reached before the specified number of characters is written into the buffer, the method returns.
Returns
A task that represents the asynchronous read operation. The value of the TResult parameter contains the total number of characters read into the buffer. The result value can be less than the number of characters requested if the number of characters currently available is less than the requested number, or it can be 0 (zero) if the end of the stream has been reached.
- Attributes
Exceptions
buffer is null.
index or count is negative.
The sum of index and count is larger than the buffer length.
The stream has been disposed.
The reader is currently in use by a previous read operation.
Remarks
The task does not complete until either the number of characters specified by the count parameter are read, or the end of the stream has been reached.
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 ReadBlock(Char[], Int32, Int32).
