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Hi! I'm currently developing a queuing system, when I executed my program a message box appeared that said "Data Type Mismatch in criteria expression". I don't have any idea what that expression means. the code below is the last line of codes I modified before the message appeared. Can anyone help me out? Thanks!

What I have tried:

If (Queue.Label1.Text <= FrmNumApp.NumCon.Text) Then
            My.Computer.Audio.Play(My.Resources.DoorBell, AudioPlayMode.Background)
            Queue.Timer4.Enabled = True
            Dim speaker2 As New SpeechSynthesizer()
            Dim speak2 As New Prosody()
            speak2.Duration = 5
            speaker2.Rate = -5
            speaker2.Volume = 100
            speaker2.Speak("Now serving number " + Queue.Label1.Text)

        ElseIf (Queue.Label1.Text > FrmNumApp.NumCon.Text) Then
            MessageBox.Show("You are calling an invalid number!")
        End If
Updated 6-Oct-17 21:27pm
Atlapure Ambrish 7-Oct-17 0:49am    
I think SelectVoiceByHints is throwing that error. Cant you debug and see which line is throwing the exception??
noob_noob 8-Oct-17 21:03pm    
I found the error. It was right here
sqlquery.Parameters.AddWithValue("@Number", Queue.Label1.Text)
I was calling a label from a different form.
Thanks anyways!

1 solution

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:
int Double(int value)
   return value * value;

Once you have an idea what might be going wrong, start using the debugger to find out why. And this is a runtime error, so it needs your code running to find more information - we can't do that as we don;t have your code, or your data. So it will be up to you.
Put a breakpoint on the first line of the method containing that code and run your app. 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?

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!
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noob_noob 8-Oct-17 21:01pm    
Hi! Thank you for this insightful comment. I will now read my codes one line at a time to understand my program better and to check if every line is doing what its supposed to be. Thanks again! You're a great help!
OriginalGriff 9-Oct-17 1:36am    
Don't just "read your codes" - use the debugger to follow what is going on while it is running! This is the most powerful tool in your toolbox, and you will spend a lot of time using it - get familiar early, and it can be an enormous help to you.

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