Exercise
Invert a text file
Objetive
Create a program to "invert" the contents of a text file: create a file with the same name ending in ".tnv" and containing the same lines as the original file but in reverse order (the first line will be the last one, the second will be the penultimate, and so on, until the last line of the original file, which should appear in the first position of the resulting file).
Hint: the easiest way, using only the programming structures we know so far, is reading the source files two times: the first time to count the amount of lines in the file, and the second time to store them in an array.
Code
Imports System
Imports System.IO
Namespace InvertText
Class Program
Private Shared Sub Main(ByVal args As String())
Console.Write("Enter name file: ")
Dim fileName As String = Console.ReadLine()
If File.Exists(fileName) Then
Dim myfileRd As StreamReader = File.OpenText(fileName)
Dim line As String
Dim countLines As Integer = 0
Do
line = myfileRd.ReadLine()
If line IsNot Nothing Then countLines += 1
Loop While line IsNot Nothing
myfileRd.Close()
Dim lines As String() = New String(countLines - 1) {}
Dim countLine As Integer = 0
myfileRd = File.OpenText(fileName)
line = ""
Do
line = myfileRd.ReadLine()
If line IsNot Nothing Then
lines(countLine) = line
countLine += 1
End If
Loop While line IsNot Nothing
myfileRd.Close()
Dim myfileWr As StreamWriter = File.CreateText(fileName & ".tnv")
For i As Integer = lines.Length - 1 To 0 + 1
myfileWr.WriteLine(lines(i))
Next
myfileWr.Close()
Else
Console.WriteLine("The file no exists.")
End If
End Sub
End Class
End Namespace