In most of the applications, you will see that file is used to store the data. The file handling term is used when different operations are performed, such as;
VB.NET provides System.IO.Fileclass, which contains static methods for operations the creation, copying, deletion, moving, and opening of a single file.
Here are the most commonly used methods of the File class which are very useful for creating and getting information about files.
| Method | Description |
|---|---|
| AppendAllLines() | Appends lines to a file, and then closes the file. If the specified file does not exist, this method creates a file, writes the specified lines to the file, and then closes the file. |
| AppendAllText() | Opens a file, appends the specified string to the file, and then closes the file. If the file does not exist, this method creates a file, writes the specified string to the file, then closes the file. |
| AppendText() | Appends text at the end of an existing file, or to a new file if the specified file does not exist. |
| Copy() | Copies an existing file to a new file. |
| Create() | Creates or overwrites a file in the specified path. |
| Delete() | Deletes the specified file. |
| Exists() | Determines whether the specified file exists. |
| Move() | Moves a specified file to a new location, providing the option to specify a new file name. |
| Open() | Opens a FileStream on the specified path with reading/write access with no sharing. |
| ReadAllLines() | Opens a text file, reads all lines of the file, and then closes the file. |
| ReadAllText() | Opens a text file, reads all the text in the file, and then closes the file. |
| ReadLines() | Reads the lines of a file. |
| Replace() | Replaces the contents of a specified file with the contents of another file, deleting the original file, and creating a backup of the replaced file. |
| WriteAllLines() | Creates a new file, writes a collection of strings to the file, and then closes the file. |
| WriteAllText() | Creates a new file and writes the contents to it. If the file already exists, it will be overwritten. |
Let's consider the following simple example, where the simple string is written to the file using the WriteAllText() method and then reads all the contents from the file using the ReadAllText() method.
Private Sub Example1()
Dim writeText As String = "This is a VB.NET Tutorial, and you are learning file handling."
'Create a file and write the content of writeText to it
File.WriteAllText("test.txt", writeText)
'Read the contents from the file
Dim readText As String = File.ReadAllText("test.txt")
Console.WriteLine(readText)
End Sub
Let's run the above code, and you will see the following output.
This is a VB.NET Tutorial, and you are learning file handling.
Let's take another example in which we will use the File class to check whether a file exists or not, if a file exists we will open the file and read data from it, if the file doesn't exist we will create a new file, write some data to it and then read all the data from that file.
Public Sub Example2()
Dim path As String = "D:\MyTest.txt"
If Not File.Exists(path) Then
Console.WriteLine("File doesn't exist, we will create a file first." & vbLf)
Using sw As StreamWriter = File.CreateText(path)
sw.WriteLine("This is a VB.NET Tutorial,")
sw.WriteLine("and you are learning")
sw.WriteLine("file handling.")
End Using
Else
Console.WriteLine("File already exists, no need to create it." & vbLf)
End If
Using sr As StreamReader = File.OpenText(path)
Dim s As String
s = sr.ReadLine()
While (s IsNot Nothing)
Console.WriteLine(s)
s = sr.ReadLine()
End While
End Using
End Sub
Let's run the above code and you will see the following output.
File doesn't exist, we will create a file first.
This is a VB.NET Tutorial,
and you are learning
file handling.
As you can see, the file doesn't exist for the first time, so first the file is created. Now, if you rerun the code, you will see that it won't create a file.
File already exists, no need to create it.
This is a VB.NET Tutorial,
and you are learning
file handling.