TextReader.ReadAsync Method

Definition

Overloads

ReadAsync(Char[], Int32, Int32)

Reads a specified maximum number of characters from the current text reader asynchronously and writes the data to a buffer, beginning at the specified index.

ReadAsync(Memory<Char>, CancellationToken)

Asynchronously reads the characters from the current stream into a memory block.

ReadAsync(Char[], Int32, Int32)

Reads a specified maximum number of characters from the current text reader asynchronously and writes the data to a buffer, beginning at the specified index.

public:
 virtual System::Threading::Tasks::Task<int> ^ ReadAsync(cli::array <char> ^ buffer, int index, int count);
public virtual System.Threading.Tasks.Task<int> ReadAsync (char[] buffer, int index, int count);
[System.Runtime.InteropServices.ComVisible(false)]
public virtual System.Threading.Tasks.Task<int> ReadAsync (char[] buffer, int index, int count);
abstract member ReadAsync : char[] * int * int -> System.Threading.Tasks.Task<int>
override this.ReadAsync : char[] * int * int -> System.Threading.Tasks.Task<int>
[<System.Runtime.InteropServices.ComVisible(false)>]
abstract member ReadAsync : char[] * int * int -> System.Threading.Tasks.Task<int>
override this.ReadAsync : char[] * int * int -> System.Threading.Tasks.Task<int>
Public Overridable Function ReadAsync (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 text is reached before the specified number of characters is read into the buffer, the current method returns.

Returns

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 text 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 text reader has been disposed.

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

Remarks

The task completes after either the number of characters specified by the count parameter are read or the end of the file is reached.

The TextReader class is an abstract class. Therefore, you do not instantiate it in your code. For an example of using the ReadAsync method, see the StreamReader.ReadAsync method.

See also

ReadAsync(Memory<Char>, CancellationToken)

Asynchronously reads the characters from the current stream into a memory block.

public virtual System.Threading.Tasks.ValueTask<int> ReadAsync (Memory<char> buffer, System.Threading.CancellationToken cancellationToken = default);
abstract member ReadAsync : Memory<char> * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<int>
override this.ReadAsync : Memory<char> * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<int>
Public Overridable Function ReadAsync (buffer As Memory(Of Char), Optional cancellationToken As CancellationToken = Nothing) As ValueTask(Of Integer)

Parameters

buffer
Memory<Char>

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

ValueTask<Int32>

A value task that represents the asynchronous read operation. The value of the type parameter contains the number of characters that have been read, or 0 if at the end of the stream and no data was read. The number will be less than or equal to the buffer length, depending on whether the data is available within the stream.

Applies to