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TextReader.ReadAsync Method

.NET Framework 4.5

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)

[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public virtual Task<int> ReadAsync(
	char[] buffer,
	int index,
	int count


Type: 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.

Type: System.Int32

The position in buffer at which to begin writing.

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.


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.

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.



.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps




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