How to create alpha-numeric barcodes in VB.NET

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I have created a barcode label printing app in vb. net using visual studio 2010. I have managed to successfully generate alpha-numeric numbers into the datagridview and the barcodes in the image column but instead of printing from 1A-1D, the barcode only prints the 1A when scanned. Please can someone tell me what I’m doing wrong, I’ve been trying to do this for the past few days, but nothing seems to work. Help much appreciated.

The code I'm using

Dim alphaNumeric As String = String.Empty
        Dim number As String = txtSubNo.Text
        Dim alphabet As String = txtAlpha.Text
        Dim loopValue As String = txtNo..Text

        For index As Integer = 0 To loopValue - 1
            alphaNumeric = number.ToString & alphabet
            pictureBox1.text = txtLabNo.text +"-" + alphaNumeric
            DataGridView1.DataSource = Nothing
            DataGridView1.ColumnCount = 4
            DataGridView1.Columns(0).Name = "LAB No"
            DataGridView1.Columns(1).Name = "SUBNO"
            DataGridView1.Columns(2).Name = "INDICATOR"
            DataGridView1.Columns(3).Name = "BARCODE"
            DataGridView1.Rows.Add(txtLabNo.Text, "" & alphaNumeric, Indicator.Text, PictureBox1.image)

            If Asc(alphabet) + 1 <= 90 Then
                alphabet = Chr(Asc(alphabet) + 1)
            Else
                alphabet = "A"

            End If

        Next
    End If

What I have tried:

I am able to add the barcode to the datagridview but the barcode only encodes for the first LabNo and alphanumeric value ie. (1A)

Posted 28-Apr-22 6:13am

Logan Govender 2021

Updated 28-Apr-22 6:44am

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The Other John Ingram 28-Apr-22 12:45pm

i think loopValue should be a int or cast via asc to a int.

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OriginalGriff · Answer 1 · 2022-04-28T06:44:00

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:

Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16

Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:

VB

Private Function Double(ByVal value As Integer) As Integer
    Return value * value
End Function

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.
This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!