Getting error IndexOutOfRangeException was unhandled - vb.net

Question

I am trying to read text from sObj.txt & write in MPadd.txt with some prefix text. The sObj.txt contains a vertical strip of words (1 in each line) & the number of lines in this file are variable (determined by user). Here is the script that I am using:
Dim commands() =
{
"stmotd -a {0}",
"stmotd -b 15 {0}"
}
Dim counter As Integer = 1
Dim objLines = File.ReadAllLines("C:\temp\sObj.txt")
Using SW As New IO.StreamWriter("c:\temp\MPadd.txt", True)
For Each line in objLines
SW.WriteLine(string.Format(commands(counter), line))
counter += 1
Next
End Using
But when executed it returns error "IndexOutOfRangeException was unhandled" also says Index was outside the bounds of the array. Please help.

Answer 1

Arrays in .NET are zero-based.
Use
Dim counter As Integer = 0
And obviously, objLines may contain no more than two lines.
Maybe you meant to emit all commands for each line?
For Each line in objLines
For Each cmd in commands
SW.WriteLine(string.Format(cmd, line))
Next
Next
EDIT:
Dim joined_lines = File.ReadAllText("C:\temp\sObj.txt").Replace(vbNewLine, " ")
Using SW As New IO.StreamWriter("c:\temp\MPadd.txt", True)
For Each cmd In commands
SW.WriteLine(String.Format(cmd, joined_lines))
Next
End Using

Answer 2

the array "commands" has only 2 items in it. When the counter value is 2, it throws an exception. I am not sure of your requirement, but you could modify your code as follows:
Dim commands() =
{
"stmotd -a {0}",
"stmotd -b 15 {0}"
}
Dim counter As Integer = 0
Dim objLines = File.ReadAllLines("C:\temp\sObj.txt")
Using SW As New IO.StreamWriter("c:\temp\MPadd.txt", True)
for Each line in objLines
If counter > 1 Then
counter = 0
End If
SW.WriteLine(string.Format(commands(counter), line))
counter += 1
Next
End Using
If you are sure of the no. of items in the commands array, I would recommend you to hard code the item index rather than using a counter variable.

Answer 3

As you only have two items in your commands array, if you import more than two lines from your file, then you'll increment counter more than twice, so you'll attempt to access an item in the array that doesn't exist, which means this line:
SW.WriteLine(string.Format(commands(counter), line))
will cause an index out of range error. Arrays in .NET are also 0 based, so counter should start at 0, unless you mean to exclude the first item in the objLines array
EDIT: Yes to do what you've mentioned in your comment you need to change it to the following:
Using SW As New IO.StreamWriter("c:\temp\MPadd.txt", True)
For Each cmd in commands
Dim strLine As New String
For Each line in objLines
strLine += " WIN" + line
Next
SW.WriteLine(String.Format(cmd, strLine.ToUpper().Trim()))
Next
End Using
This will append all items in your array to a single line with a WIN prefix:
stmotd -a WINFPH WINMAC WINPPC WINVPN
stmotd -b 15 WINFPH WINMAC WINPPC WINVPN