TextReader.ReadBlockAsync Method
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
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.
Namespace: System.IO
Assembly: mscorlib (in mscorlib.dll)
Syntax
Public Overridable Function ReadBlockAsync ( _
buffer As Char(), _
index As Integer, _
count As Integer _
) As Task(Of Integer)
public virtual Task<int> ReadBlockAsync(
char[] buffer,
int index,
int count
)
Parameters
- buffer
Type: array<System..::.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
Type: System..::.Int32
The position in buffer at which to begin writing.
- count
Type: System..::.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.
Return Value
Type: System.Threading.Tasks..::.Task<(Of <(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.
Exceptions
| Exception | Condition |
|---|---|
| ArgumentNullException | buffer is nullNothingnullptra null reference (Nothing in Visual Basic). |
| ArgumentOutOfRangeException | index or count is negative. |
| ArgumentException | The sum of index and count is larger than the buffer length. |
| ObjectDisposedException | The text reader has been disposed. |
| InvalidOperationException | 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 text has been reached.
Version Information
Windows Phone OS
Supported in: 8.1, 8.0