TextReader::ReadBlockAsync Method
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)
[ComVisibleAttribute(false)] [HostProtectionAttribute(SecurityAction::LinkDemand, ExternalThreading = true)] public: virtual Task<int>^ ReadBlockAsync( array<wchar_t>^ 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<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.
| Exception | Condition |
|---|---|
| ArgumentNullException | buffer is nullptr. |
| 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. |
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.
.gif?cs-save-lang=1&cs-lang=cpp "Note") Note |
|---|
The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: ExternalThreading. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes. |
Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
