This documentation is archived and is not being maintained.

FileStream::Read Method

Reads a block of bytes from the stream and writes the data in a given buffer.

Namespace:  System.IO
Assembly:  mscorlib (in mscorlib.dll)

virtual int Read(
	[InAttribute] [OutAttribute] array<unsigned char>^ array, 
	int offset, 
	int count
) override


Type: array<System::Byte>
When this method returns, contains the specified byte array with the values between offset and (offset + count - 1) replaced by the bytes read from the current source.
Type: System::Int32
The byte offset in array at which the read bytes will be placed.
Type: System::Int32
The maximum number of bytes to read.

Return Value

Type: System::Int32
The total number of bytes read into the buffer. This might be less than the number of bytes requested if that number of bytes are not currently available, or zero if the end of the stream is reached.


array is nullptr.


offset or count is negative.


The stream does not support reading.


An I/O error occurred.


offset and count describe an invalid range in array.


Methods were called after the stream was closed.

This method overrides Read.

The offset parameter gives the offset of the byte in array (the buffer index) at which to begin reading, and the count parameter gives the maximum number of bytes to be read from this stream. The returned value is the actual number of bytes read, or zero if the end of the stream is reached. If the read operation is successful, the current position of the stream is advanced by the number of bytes read. If an exception occurs, the current position of the stream is unchanged.

The Read method returns zero only after reaching the end of the stream. Otherwise, Read always reads at least one byte from the stream before returning. If no data is available from the stream upon a call to Read, the method will block until at least one byte of data can be returned. An implementation is free to return fewer bytes than requested even if the end of the stream has not been reached.

Use BinaryReader for reading primitive data types.

Interrupting a thread that is performing a read operation is not supported. Although the operations may appear to be successful after the thread is unblocked, these actions can decrease your application's performance and reliability.

For a list of common I/O tasks, see Common I/O Tasks.

The following example reads the contents from a FileStream and writes it into another FileStream.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.