循环浏览文本文件中的内容

Question

New TechGuy on this site. Thought i'd make this resourceful since im getting ready to graduate and want more programming practice. I have a question:

I tried looping through a text file I created and I wanted to replace each multiple of 3 with the word "changed". I created a text file and entered numbers 1-15 on each line. My code is below but for some reason it would only change the number 3 and 13. I tried using this link as a resource ( Loop through the lines of a text file in VB.NET ) but that wasnt to helpful. Anyway here is my code, can someone help with what i'm doing wrong?

Public Class numbers

  Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load


    Dim OpenFilePrompt As New OpenFileDialog
    openFilePrompt.ShowDialog()
    Dim currentReader As New System.IO.StreamReader(OpenFilePrompt.FileName)
    txtInput.Text = currentReader.ReadToEnd

    Dim a As String

    Dim numbers As New List(Of String)

    a = txtInput.Text
    numbers.Add(a)

    Dim b As Integer

    For i = 0 To numbers.Count Step 3
        b = b + 3

        TextBox2.Text = (numbers.Item(i).Replace(b.ToString, "Changed"))

    Next


  End Sub


End Class 

Answer 1

You are setting numbers (the first item) to a , which is txtInput.Text . Then you have a one size list which is completely useless!

You should use Mod instead.

Divides two numbers and returns only the remainder.

So just check if Integer Mod 3 equals 0 .

Also consider using File.ReadAllLines(String) , Val(String) , String.Join(String, String()) and File.WriteAllLines(String, String()) .

Dim Content() As String = File.ReadAllLines(OpenFilePrompt.FileName)
For Index As Integer = 0 To Content.Length - 1
    Dim Number As Integer = Val(Content(Index))
    If Number Mod 3 = 0 Then
        Content(Index) = "changed"
    End If
Next
txtInput.Text = String.Join(vbCrLf, Content)
File.WriteAllLines(OpenFilePrompt.FileName, Content)