vb.net readalllines fill form replace certain lines coding advice - vb.net

Question

What I'm trying to accomplish is reading a text file and selecting certain lines to modify by filling in text from a second form. Here is an example the code I'm currently using. What's happening is I'm looking for a line that starts with 718 and then somewhere after that line there will be a line that starts with 720. I need both lines to fill in the second form. The only way I can think of is to just keep adding 1 to the line until it reaches the line I need. I'm still new to this and I'm sure there's an easier way to do this maybe using Try or While but I'm not sure how. Appreciate any help.
Dim lines() As String = File.ReadAllLines(tempsave)
For i As Integer = 0 To lines.Length - 1
If lines(i).StartsWith("718") Then
If lines(i + 1).StartsWith("720") Then
Dim array() As String = lines(i).Split("*"c, "~"c)
Dim array2() As String = lines(i + 1).Split("*"c, "~"c)
FormFill.TextBox1.Text = array(3)
FormFill.TextBox2.Text = array(9)
FormFill.ShowDialog()
lines(i) = lines(i).Replace(array(3), FormFill.TextBox1.Text)
lines(i + 1) = lines(i + 1).Replace(array(9), FormFill.TextBox2.Text)
Else
If lines(i + 2).StartsWith("720") Then
Dim array() As String = lines(i).Split("*"c, "~"c)
Dim array2() As String = lines(i + 2).Split("*"c, "~"c)
FormFill.TextBox1.Text = array(3)
FormFill.TextBox2.Text = array(9)
FormFill.ShowDialog()
lines(i) = lines(i).Replace(array2(3),FormFill.TextBox1.Text)
lines(i + 2) = lines(i + 2).Replace(array(9), FormFill.TextBox2.Text)
End If
End If
End If
Next
Example Data:
Input:
123*test*test*test~
718*test*test*test~
543*test*test*test~
720*test*test*test~
Output:
123*test*test*test~
718*test*test*newdata~
543*test*test*test~
720*test*test*newdata~

Answer 1

Here, try this:
Public Sub Lines()
Dim _
aNextLines,
aAllLines As String()
Dim _
s718Line,
s720Line As String
aAllLines = IO.File.ReadAllLines("D:\Logs\Data.log")
For i As Integer = 0 To aAllLines.Length - 1
If aAllLines(i).StartsWith("718") Then
s718Line = aAllLines(i)
aNextLines = aAllLines.Skip(i + 1).ToArray
s720Line = aNextLines.FirstOrDefault(Function(Line) Line.StartsWith("720"))
' Process data here
End If
Next
End Sub
--UPDATE--
Here's a modified version that both reads and writes:
Public Sub Lines()
Dim oForm As FormFill
Dim _
aNextLines,
aAllLines As String()
Dim _
i718Index,
i720Index As Integer
Dim _
s718Line,
s720Line As String
oForm = New FormFill
aAllLines = IO.File.ReadAllLines(oForm.FilePath)
s718Line = String.Empty
s720Line = String.Empty
For i718Index = 0 To aAllLines.Length - 1
If aAllLines(i718Index).StartsWith("718") Then
s718Line = aAllLines(i718Index)
aNextLines = aAllLines.Skip(i718Index + 1).ToArray
For i720Index = 0 To aNextLines.Length - 1
If aNextLines(i720Index).StartsWith("720") Then
s720Line = aNextLines(i720Index)
Exit For ' Assumes only one 720 line in the file
End If
Next
Exit For ' Assumes only one 718 line in the file
End If
Next
oForm.TextBox718.Text = s718Line
oForm.TextBox720.Text = s720Line
oForm.TextBox718.Tag = i718Index
oForm.TextBox720.Tag = i720Index
End Sub
Now, in your Save button's Click event handler:
Private Sub SaveButton_Click(Sender As Button, e As EventArgs) Handles SaveButton.Click
Dim aAllLines As String()
Dim _
i718Index,
i720Index As Integer
Dim _
s718Line,
s720Line As String
s718Line = Me.TextBox718.Text
s720Line = Me.TextBox720.Text
i718Index = Me.TextBox718.Tag
i720Index = Me.TextBox720.Tag
aAllLines = IO.File.ReadAllLines(Me.FilePath)
aAllLines(i718Index) = s718Line
aAllLines(i720Index) = s720Line
IO.File.WriteAllLines(Me.FilePath, aAllLines)
End Sub
That should do it.