“Input string was not in a correct format” while parsing the content of a file - vb.net

Question

I need help, I don't know why the array for the quantity in my input file strArr(1) having an error that says that the input string was not in a correct format.
Dim objReader As IO.StreamReader
Dim objWriter As New IO.StreamWriter("C:\Users\user\Desktop\StationeryFolder\output.txt")
Dim strLine As String
Dim strName As String
Dim intQuantity As Integer
Dim intTotal As Integer
Dim strArr() As String
If IO.File.Exists("C:\Users\user\Desktop\StationeryFolder\input.txt") = True Then
objReader = IO.File.OpenText("C:\Users\user\Desktop\StationeryFolder\input.txt")
Else
MsgBox("File is not exist")
Close()
End If
Do While objReader.Peek <> -1
strLine = objReader.ReadLine()
strArr = strLine.Split(" ")
strName = strArr(0)
intQuantity = Convert.ToInt32(strArr(1)) //this is where the error occurs
intTotal = intTotal + intQuantity
lstDisplay.Items.Add(strName & " " & intQuantity.ToString())
objWriter.WriteLine(strName & " " & intQuantity.ToString())
Loop
lstDisplay.Items.Add("Total Quantity of Stationeries are: " & intTotal.ToString())
objWriter.WriteLine("Total Quantity of Stationeries are: " & intTotal.ToString())
objReader.Close()
objWriter.Close()
Inside the input file:
Markers
15
Pens
25

Answer 1

I used the .net File class instead of streams. ReadAllLine returns an array of the lines in the file. I used a StringBuilder which is mutable (changeable) unlike a String. Saves the code from creating and throwing away several strings. I have used interpolated strings indicated by the $ before the quotes. This allows inserting variables directly into the string surrounded by braces.
Private Sub OPCode()
Dim inputPath = "C:\Users\user\Desktop\StationeryFolder\input.txt"
If Not IO.File.Exists(inputPath) Then
MsgBox("File does not exist")
Close()
End If
Dim lines = File.ReadAllLines(inputPath)
Dim total As Integer
Dim sb As New StringBuilder
For i = 0 To lines.Length - 2 Step 2
lstDisplay.Items.Add($"{lines(i)} {lines(i + 1)}")
sb.AppendLine($"{lines(i)} {lines(i + 1)}")
total += CInt(lines(i + 1))
Next
lstDisplay.Items.Add($"Total Quantity of Stationeries are: {total}")
sb.AppendLine($"Total Quantity of Stationeries are: {total}")
File.WriteAllText("C:\Users\user\Desktop\StationeryFolder\output.txt", sb.ToString)
End Sub