Binary files are a sequence of bytes stored for future use. They could contain images, text, programs, data or anything else. The binary file routines can read/write any byte (or sequence of bytes) in the file without reading the previous bytes. When accessing any file (including binary) you should enclose the function in a Try...Catch block and try to handle unexpected errors e.g. disk full or file locked.
 
You can use these Binary File functions with any type of file, including Text and CSV files. Although some text files use one byte per letter, many formats require 2 bytes per letter. The binary reader pulls data 1 byte at a time and your program may need code to interpret 2 byte characters
 
Avoid editing any biinary file unless you fully understand the file format. It is very easy to render the file permenantly unreadable.
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Private Function ReadBinary_FirstBytes(filename As String, NumberOfBytes As Integer) As List(Of Byte)
 Dim bytesRead As Integer
 Dim buffer(NumberOfBytes) As Byte 'Default buffer size is 4096
 Using inFile As New IO.FileStream(filename, FileMode.Open)
  bytesRead = inFile.Read(buffer, 0, buffer.Length)
 End Using
 Return buffer.ToList
End Function
  

Private Sub ReadBinary_BlockAtATime(filename As String, blockSize As Integer)
 Dim buffer(blockSize - 1) As Byte
 Dim bytesRead As Integer = 9999 ' dummy value > 0
 Using stream As New IO.FileStream(filename, FileMode.Open)
  While bytesRead > 0
   bytesRead = stream.Read(Buffer, 0, Buffer.Length)
   If bytesRead > 0 Then
    '
    ' add logic to process the current block of date here
    '
   End If
  End While
 End Using
End Sub
  

Private Function ReadBinary_MiddleOfFile(filename As String, startPosition As Integer, numberOfBytes As Integer) As List(Of Byte)
 Using stream = File.OpenRead(filename)
  stream.Position = startPosition
  Dim bytes(numberOfBytes - 1) As Byte
  stream.ReadExactly(bytes, startPosition, numberOfBytes)
  Return bytes.ToList
 End Using
End Function
  

Consider checking file size before asking computer to read an entire file. It could attempt to drop entire contents of huge (> 4GB) file into memory!

Private Function ReadBinary_AllBytes(filename As String) As List(Of Byte)
 Return IO.File.ReadAllBytes(filename).ToList
End Function
  

File corruption is a common occurence when trying to overwrite part of a binary file. You should ensure that you fully understand te hfile format and consequences of your changes. Suppose we have a simple binary file whose contents are

   Daniel1Freda 2Joe   3Mike  4
  

The file format is 6 bytes for the name, 1 byte for the number. We realise that Joe wants to be called Josephine and overwrite the name. Our file now contains

   Daniel1Freda 2Josephineke  4
  

the file is corrupted - the computer will see an "i" instead of Joe's number and "neke" instead of "Mike"

Private Sub OverwriteBinary_MiddleOfFile(filename As String, startPosition As Integer, ListBytes As List(Of Byte))
 Using stream = File.OpenWrite(filename)
  stream.Position = startPosition
  stream.Write(ListBytes.ToArray)
 End Using
End Sub
  

Private Sub Append(filename As String, ListBytes As List(Of Byte))
 Using fs As New IO.FileStream(filename, IO.FileMode.Append)
  Using bw As New IO.BinaryWriter(fs)
   bw.Write(ListBytes.ToArray)
  End Using
 End Using
End Sub
  

Private Sub WriteBinary_AllBytes(filename As String, ListBytes As List(Of Byte))
    IO.File.WriteAllBytes(filename, ListBytes.ToArray)
End Sub
  

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