Files Handling in .NET

Files in VB .NET

Working with Files

File handling in Visual Basic is based on System.IO namespace with a class library that supports string, character and file manipulation. These classes contain properties, methods and events for creating, copying, moving, and deleting files. Since both strings and numeric data types are supported, they also allow us to incorporate data types in files. The most commonly used classes are FileStream, BinaryReader, BinaryWriter, StreamReader and StreamWriter.

FileStream Class

This class provides access to standard input and output files. We use the members of FileAccess, FileMode and FileShare Enumerations with the constructors of this class to create or open a file. After a file is opened it's FileStream object can be passed to the Binary Reader, BinaryWriter, Streamreader and StreamWriter classes to work with the data in the file. We can also use the FileStreamSeek method to move to various locations in a file which allows to break a file into records each of the same length.

StreamReader and StreamWriter Class

The StreamReader and StreamWriter classes enables us to read or write a sequential stream of characters to or from a file.

BinaryReader and BinaryWriter Class

The BinaryReader and BinaryWriter classes enable us to read and write binary data, raw 0's and 1's, the form in which data is stored on the computer.

The following examples puts some code to work with textual data using FileStream and StreamReader and StreamWriter classes.

Code to create a File

Imports System.IO 'NameSpace required to be imported to work with files Public Class Form1 Inherits System.Windows.Forms.Form Private Sub Form1_Load(ByVal sender As System.Object, ByVal e_ As System.EventArgs) Handles MyBase.Load Dim fs as New FileStream("file.doc", FileMode.Create, FileAccess.Write) 'declaring a FileStream and creating a word document file named file with 'access mode of writing Dim s as new StreamWriter(fs) 'creating a new StreamWriter and passing the filestream object fs as argument s.BaseStream.Seek(0,SeekOrigin.End) 'the seek method is used to move the cursor to next position to avoid text to be 'overwritten s.WriteLine("This is an example of using file handling concepts in VB .NET.") s.WriteLine("This concept is interesting.") 'writing text to the newly created file s.Close() 'closing the file End Sub End Class

The default location where the files we create are saved is the bin directory of the Windows Application with which we are working.
Code to create a file and read from it

Drag a Button and a RichTextBox control onto the form. Paste the following code which is shown below.

Imports System.IO 'NameSpace required to be imported to work with files Public Class Form1 Inherits System.Windows.Forms.Form Private Sub Button1_Click(ByVal....., Byval.....)Handles Button1.Click Dim fs as New FileStream("file.doc", FileMode.Create, FileAccess.Write) 'declaring a FileStream and creating a document file named file with 'access mode of writing Dim s as new StreamWriter(fs) 'creating a new StreamWriter and passing the filestream object fs as argument s.WriteLine("This is an example of using file handling concepts in VB .NET.") s.WriteLine("This concept is interesting.") 'writing text to the newly created file s.Close() 'closing the file fs=New FileStream("file.doc",FileMode.Open,FileAccess.Read) 'declaring a FileStream to open the file named file.doc with access mode of reading Dim d as new StreamReader(fs) 'creating a new StreamReader and passing the filestream object fs as argument d.BaseStream.Seek(0,SeekOrigin.Begin) 'Seek method is used to move the cursor to different positions in a file, in this code, to 'the beginning while d.peek()>-1 'peek method of StreamReader object tells how much more data is left in the file RichTextbox1.Text &= d.readLine() 'displaying text from doc file in the RichTextBox End while d.close() End Sub

Working with Directories

We will work with the File and Directory classes in this section. We will create a directory and copy a file into the newly created directory.

File Class

The File class in VB .NET allows us to work with files, allowing to copy, delete and create files.

Directory Class

The Directory class in VB .NET allows us to create and work with Folders/Directories. With this class we can create, edit and delete folders and also maintain drives on the machine.

Code to work with File and Directory Class

The following code will create a directory and copy a file into that new directory. To create a new directory we should use the Directory class's CreateDirectory method. Drag two Button's (Button1, Button2), a TextBox and a OpenFileDialog control from the toolbar onto the Form. We will use the TextBox to specify a location to create the Directory when Button1 is clicked and the OpenFileDialog control to open a file and copy it into the newly created Directory when Button2 is clicked. The namespace to be imported is System.IO. The code for that looks like this:

Imports System.IO Public Class Form1 Inherits System.Windows.Forms.Form  'Windows Form Designer Generated Code Private Sub Form1_Load(ByVal sender As System.Object, ByVal e _ As System.EventArgs) Handles MyBase.Load End Sub Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As_ System.EventArgs) Handles Button1.Click Try Directory.CreateDirectory(TextBox1.Text)  'Creating a directory by specifying a path in the TextBox, of the form c:\examples 'Instead of using a TextBox you can directly type the location of the directory like this 'Directory.CreateDirectory("c:\examples") Catch End Try MsgBox("Done") End Sub Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As _ System.EventArgs) Handles Button2.Click Try If OpenFileDialog1.ShowDialog <> DialogResult.Cancel Then File.Copy(OpenFileDialog1.FileName, TextBox1.Text & "\" & _ OpenFileDialog1.FileName.Substring(OpenFileDialog1.FileName.LastIndexOf("\"))) 'The above line of code uses OpenFileDialog control to open a dialog box where you 'can select a file to copy into the newly created directory End If Catch End Try MsgBox("File Copied Successfully") End Sub End Class

That's all it takes to create a directory and copy a file into the newly created directory in VB.NET.