VB.Net - File Handling

A file is a collection of data stored in a disk with a specific name and a directory path. When a file is opened for reading or writing, it becomes a stream.
The stream is basically the sequence of bytes passing through the communication path. There are two main streams: the input stream and the output stream. The input stream is used for reading data from file (read operation) and the output stream is used for writing into the file (write operation).
The System.IO namespace has various classes that are used for performing various operations with files, like creating and deleting files, reading from or writing to a file, closing a file, etc.
The following table shows some commonly used non-abstract classes in the System.IO namespace −
The FileStream class in the System.IO namespace helps in reading from, writing to and closing files. This class derives from the abstract class Stream.
You need to create a FileStream object to create a new file or open an existing file. The syntax for creating a FileStream object is as follows −
Dim <object_name> As FileStream = New FileStream(<file_name>, <FileMode Enumerator>, <FileAccess Enumerator>, <FileShare Enumerator>)

For example, for creating a FileStream object F for reading a file named sample.txt −
Dim f1 As FileStream = New FileStream("sample.txt", FileMode.OpenOrCreate, FileAccess.ReadWrite)

The FileMode enumerator defines various methods for opening files. The members of the FileMode enumerator are −
Append − It opens an existing file and puts cursor at the end of file, or creates the file, if the file does not exist.
Append − It opens an existing file and puts cursor at the end of file, or creates the file, if the file does not exist.
Create − It creates a new file.
Create − It creates a new file.
CreateNew − It specifies to the operating system that it should create a new file.
CreateNew − It specifies to the operating system that it should create a new file.
Open − It opens an existing file.
Open − It opens an existing file.
OpenOrCreate − It specifies to the operating system that it should open a file if it exists, otherwise it should create a new file.
OpenOrCreate − It specifies to the operating system that it should open a file if it exists, otherwise it should create a new file.
Truncate − It opens an existing file and truncates its size to zero bytes.
Truncate − It opens an existing file and truncates its size to zero bytes.
FileAccess enumerators have members: Read, ReadWrite and Write.
FileShare enumerators have the following members −
Inheritable − It allows a file handle to pass inheritance to the child processes
Inheritable − It allows a file handle to pass inheritance to the child processes
None − It declines sharing of the current file
None − It declines sharing of the current file
Read − It allows opening the file for reading
Read − It allows opening the file for reading
ReadWrite − It allows opening the file for reading and writing
ReadWrite − It allows opening the file for reading and writing
Write − It allows opening the file for writing
Write − It allows opening the file for writing
The following program demonstrates use of the FileStream class −
Imports System.IO
Module fileProg
   Sub Main()
      Dim f1 As FileStream = New FileStream("sample.txt", _ FileMode.OpenOrCreate, FileAccess.ReadWrite)
      Dim i As Integer
      
      For i = 0 To 20
         f1.WriteByte(CByte(i))
      Next i
      f1.Position = 0
      
      For i = 0 To 20
         Console.Write("{0} ", f1.ReadByte())
      Next i
      f1.Close()
      Console.ReadKey()
   End Sub
End Module
When the above code is compiled and executed, it produces the following result −
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 -1

The preceding example provides simple file operations in VB.Net. However, to utilize the immense powers of System.IO classes, you need to know the commonly used properties and methods of these classes.
We will discuss these classes and the operations they perform in the following sections. Please click the links provided to get to the individual sections −
Reading from and Writing into Text files
It involves reading from and writing into text files. The StreamReader and StreamWriter classes help to accomplish it.
Reading from and Writing into Binary files
It involves reading from and writing into binary files. The BinaryReader and BinaryWriter classes help to accomplish this.
Manipulating the Windows file system
It gives a VB.Net programmer the ability to browse and locate Windows files and directories.

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