Stream.Read Method

When overridden in a derived class, reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read.

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

'Declaration
Public MustOverride Function Read ( _
	<OutAttribute> buffer As Byte(), _
	offset As Integer, _
	count As Integer _
) As Integer
'Usage
Dim instance As Stream 
Dim buffer As Byte()
Dim offset As Integer 
Dim count As Integer 
Dim returnValue As Integer 

returnValue = instance.Read(buffer, offset, _
	count)

Parameters

buffer
Type: System.Byte()

An array of bytes. When this method returns, the buffer contains the specified byte array with the values between offset and (offset + count - 1) replaced by the bytes read from the current source.

offset
Type: System.Int32

The zero-based byte offset in buffer at which to begin storing the data read from the current stream.

count
Type: System.Int32

The maximum number of bytes to be read from the current stream.

Return Value

Type: System.Int32
The total number of bytes read into the buffer. This can be less than the number of bytes requested if that many bytes are not currently available, or zero (0) if the end of the stream has been reached.

ExceptionCondition
ArgumentException

The sum of offset and count is larger than the buffer length.

ArgumentNullException

buffer is Nothing.

ArgumentOutOfRangeException

offset or count is negative.

IOException

An I/O error occurs.

NotSupportedException

The stream does not support reading.

ObjectDisposedException

Methods were called after the stream was closed.

Use the CanRead property to determine whether the current instance supports reading.

Implementations of this method read a maximum of count bytes from the current stream and store them in buffer beginning at offset. The current position within the stream is advanced by the number of bytes read; however, if an exception occurs, the current position within the stream remains unchanged. Implementations return the number of bytes read. The return value is zero only if the position is currently at the end of the stream. The implementation will block until at least one byte of data can be read, in the event that no data is available. Read returns 0 only when there is no more data in the stream and no more is expected (such as a closed socket or end of file). An implementation is free to return fewer bytes than requested even if the end of the stream has not been reached.

Additional calls to Read may be required in network operations if all the data was not downloaded.

Use BinaryReader for reading primitive data types.

The following example shows how to use Read to read a block of data.

Imports System
Imports System.IO

Public Class Block
    Public Shared Sub Main()
        Dim s As Stream = New MemoryStream()
        For i As Integer = 0 To 99
            s.WriteByte(CType(i, Byte))
        Next i
        s.Position = 0

        ' Now read s into a byte buffer. 
        Dim bytes(s.Length) As Byte
        Dim numBytesToRead As Integer = s.Length
        Dim numBytesRead As Integer = 0
        Dim n As Integer 
        While numBytesToRead > 0
            ' Read may return anything from 0 to 10.
            n = s.Read(bytes, numBytesRead, 10)
            ' The end of the file is reached. 
            If n = 0 Then 
                Exit While 
            End If
            numBytesRead += n
            numBytesToRead -= n
        End While
        s.Close()
        ' numBytesToRead should be 0 now, and numBytesRead should 
        ' equal 100.
        Console.WriteLine("number of bytes read: {0:d}", numBytesRead)
    End Sub 
End Class

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

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

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0
Was this page helpful?
(1500 characters remaining)
Thank you for your feedback

Community Additions

ADD
Show:
© 2014 Microsoft