Microsoft Visual Basic 2010 Step by Step eBook

316 Part II Programming Fundamentals

Because of this speed factor, the My namespace provides an excellent shortcut to many

common programming tasks. It is important to take note of this feature and its possible uses,

but the My namespace is efficient here because we are reading the entire text file.

If you forget the syntax for the ReadAllText method, you can quickly insert an example by

using the Insert Snippet command. As described in Chapter 7, “Using Loops and Timers,“

the Insert Snippet command allows you to insert common code snippets in the Code

Editor. To insert the ReadAllText method, display the Code Editor, and on the Edit menu,

click IntelliSense, and then click Insert Snippet. In the Insert Snippet list box, double-click

Fundamentals – Collections, Data Types, File System, Math; double-click File System –

Processing Drives, Folders, And Files; and then double-click Read Text From A File. This

inserts the following code snippet:

Dim fileContents1 As String

fileContents1 = My.Computer.FileSystem.ReadAllText("C:\Test.txt")

The StreamReader Class

The StreamReader class in the .NET Framework library allows you to open and display text

files in your programs. I’ll use this technique several times in this book when I work with text

files (for example, in Chapter 16, “Inheriting Forms and Creating Base Classes”). To make it

easier to use the StreamReader class, you add the following Imports statement to the top

of your code, as discussed in Chapter 5, “Visual Basic Variables and Formulas, and the .NET

Framework”:

Imports System.IO

Then, if your program contains a text box object, you can display a text file inside the text

box by using the following program code. (The text file opened in this example is Badbills .txt,

and the code assumes that an object named TextBox1 has been created on your form .)

Dim StreamToDisplay As StreamReader

StreamToDisplay = New StreamReader("C:\vb10sbs\chap13\text browser\badbills.txt")

TextBox1.Text = StreamToDisplay.ReadToEnd

StreamToDisplay.Close()

In this StreamReader example, I declare a variable named StreamToDisplay of the type

StreamReader to hold the contents of the text file, and then I specify a valid path for the file

I want to open. Next, I read the contents of the text file into the StreamToDisplay variable

by using the ReadToEnd method, which retrieves all the text in the file from the current

location (the beginning of the text file) to the end of the text file and assigns it to the Text

property of the text box object. The final statement closes the StreamReader. Closing the