Visual Basic 2012 Programmer's Reference

OPENTEXT, CREATETEXT, AND APPENDTEXT

The File class in the System.IO namespace provides four shared methods that are particularly useful for working with StreamReader and StreamWriter objects associated with text files. The following table summarizes these four methods.

METHOD	PURPOSE
Exists	Returns True if a file with a given path exists.
OpenText	Returns a StreamReader that lets you read from an existing text file.
CreateText	Creates a new text file, overwriting any existing file at the given path, and returns a StreamWriter that lets you write into the new file.
AppendText	If the indicated file does not exist, creates the file. Whether the file is new or previously existing, returns a StreamWriter that lets you append text at the end of the file.

The OpenCreateAppendText example program lets you open an existing file, create a new file, or append text at the end of an existing file. It uses the following code to demonstrate the Exists and OpenText methods:

Dim file_name As String = Application.StartupPath & "\test.txt"
If Not Exists(file_name) Then
    txtData.Text = " < File not found > "
Else
    Using sr As StreamReader = OpenText(file_name)
        txtData.Text = sr.ReadToEnd()
        sr.Close()
    End Using
End If

This code uses Exists to see if the file exists. If the file does exist, the code uses OpenText to open the file and get a StreamReader associated with it. It uses the StreamReader class’s ReadToEnd method to display the file’s text in the text box txtData.

The OpenCreateAppendText ...