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 following table shows some commonly used non-abstract classes in the System.IO namespace:
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:
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:
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).
VB.Net I/O Classes
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:
I/O Class | Description |
---|---|
BinaryReader | Reads primitive data from a binary stream. |
BinaryWriter | Writes primitive data in binary format. |
BufferedStream | A temporary storage for a stream of bytes. |
Directory | Helps in manipulating a directory structure. |
DirectoryInfo | Used for performing operations on directories. |
DriveInfo | Provides information for the drives. |
File | Helps in manipulating files. |
FileInfo | Used for performing operations on files. |
FileStream | Used to read from and write to any location in a file. |
MemoryStream | Used for random access of streamed data stored in memory. |
Path | Performs operations on path information. |
StreamReader | Used for reading characters from a byte stream. |
StreamWriter | Is used for writing characters to a stream. |
StringReader | Is used for reading from a string buffer. |
StringWriter | Is used for writing into a string buffer. |
The FileStream Class
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)
Parameter | Description |
---|---|
FileMode |
The FileMode enumerator defines various methods for opening files. The members of the FileMode enumerator are:
|
FileAccess |
FileAccess enumerators have members: Read, ReadWrite and Write. |
FileShare |
FileShare enumerators have the following members:
|
Example:
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 ModuleWhen 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
Advanced File Operations in VB.Net
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:
Topic and Description |
---|
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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