How to dislay mismatch lines when comparing two text files? - vb.net

Question

I'm new to VB.Net. I've implemented scripting to compare two text files that checks if the value or data is different from each other. The only problem is it shows only one line instead of two
Below is the data that is in text A and C:
Text A: Orange,Apple,Mango,Strawberry,Banana
Text B: Orange, Apple, Mango, Blueberry, Grapes
Here is my script
Sub Main()
Const ForReading = 1
Dim objFile1, objFile2, objFile3
Dim objFSO = CreateObject("Scripting.FileSystemObject")
objFile1 = objFSO.OpenTextFile("C:\Scripts\A.txt", ForReading) 'Current.txt represents Text from AWS network
Dim strAddresses, strCurrent, strNoAddress
strAddresses = objFile1.ReadAll
objFile1.Close()
objFile2 = objFSO.OpenTextFile("C:\Scripts\C.txt", ForReading) 'Current.txt represents Text from Shell network
Do Until objFile2.AtEndOfStream
strCurrent = objFile2.ReadLine
If InStr(strAddresses, strCurrent) = 0 Then
strNoAddress = strCurrent & vbCrLf
End If
Loop
objFile2.Close()
objFile3 = objFSO.CreateTextFile("C:\Scripts\Differences.txt")
objFile3.WriteLine(strNoAddress)
objFile3.Close()
End Sub

Answer 1

Your code does not work because you overwrite strNoAddress everytime the if conditions is true:
strNoAddress = strCurrent & vbCrLf
So when you hit Blueberry, strNoAddress becomes Blueberry\n.
When you hit Grapes, strNoAddress becomes Grapes\n instead of Blueberry\nGrapes\n.
You want to concatenate the strings instead:
strNoAddress &= strCurrent & vbCrLf
A more "up-to-date" version of your code without the legacy/leftover functions of VB6 could look like:
Dim addresses = File.ReadAllLines("C:\Scripts\A.txt")
Dim noAdress = String.Empty
Using reader = new StreamReader("C:\Scripts\B.txt")
Do Until reader.EndOfStream
Dim current = reader.ReadLine
If Not addresses.Contains(current) Then
noAdress &= current & Environment.NewLine
End If
Loop
End Using
...
Or, to make it even more simple (good enough for small files, and without a trainling newline):
Dim fileA = File.ReadAllLines("C:\Scripts\A.txt")
Dim fileB = File.ReadAllLines("C:\Scripts\B.txt")
Dim noAdress = String.Join(Environment.NewLine, fileB.Where(Function(b) Not fileA.Contains(b)))