Microsoft Visual Basic 2010 Step by Step eBook

346 Part II Programming Fundamentals

To Do This

Write a text file

by using the My

namespace

Use the My.Computer.FileSystem object and the WriteAllText method. For

example (assuming that you are also using a save file dialog object named

sfd and a text box object named txtNote):

sfd.Filter = "Text files (*.txt)|*.txt"

If sfd.ShowDialog() = DialogResult.OK Then

My.Computer.FileSystem.WriteAllText( _

sfd.FileName, txtNote.Text, False)

End If

Write a text file

by using the

StreamWriter class

Add the statement Imports System.IO to your form’s declaration section,

and then use StreamWriter. Use the Write method to write the text. When

finished, call the Close method. For example, to write the contents of a text

box object named TextBox1 to a file:

Dim StreamToWrite As StreamWriter

StreamToWrite = New StreamWriter( _

"c:\vb10sbs\chap13\output.txt")

StreamToWrite.Write(TextBox1.Text)

StreamToWrite.Close()

Write a text file line

by line

Use StreamWriter and the WriteLine method. Use the OpenTextFileWriter

method in the My namespace to open a StreamWriter:

Dim LineOfText As String = ""

Dim StreamToWrite As StreamWriter

StreamToWrite = My.Computer.FileSystem.OpenTextFileWriter( _

"C:\vb10sbs\chap13\output.txt", False)

LineOfText = InputBox("Enter line")

Do Until LineOfText = ""

StreamToWrite.WriteLine(LineOfText)

LineOfText = InputBox("Enter line")

Loop

StreamToWrite.Close()

Process strings Use the String class. Some of the members of String include:

n Compare

n CompareTo

n Contains

n EndsWith

n IndexOf

n Insert

n Length

Convert a string

with separators to

an array

Use the Split method on the String class. For example:

Dim AllText As String = "a*b*c*1*2*3"

Dim strArray() As String

strArray = AllText.Split("*")

'strArray = {"a", "b", "c", "1", "2", "3"}

n Remove

n Replace

n StartsWith

n Substring

n ToLower

n ToUpper

n Trim