Problems with "running" functionality - vb.net

Question

I am a new programmer learning Visual Basic.
Right now, I'm working on a project about a softball scoreboard. I have been working on this project for a bit, and I am confused on 1 thing.
The thing I am confused on is that I put in a messagebox that said invalid input for negative numbers, but it does not delete it from lstScores and even though the message box appears it still counts as a inning input.
If runs < 0 Then
MessageBox.Show(VALID_MESSAGE)
This is the code:
Public Class frmSoftballScoreboard
Const VALID_MESSAGE As String = "Enter valid runs value"
Const ONLY_MESSAGE As String = "Only seven innings are allowed"
'Declaring array
Dim scores(6) As Double
'declaring variables
Dim runs As String
Dim runningScore As Integer = 0
Dim i As Integer = 0
Dim out As Double
'page load event
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
lstScores.Items.Add("Runs : Running Score")
End Sub
'Enter score button
Private Sub btnScore_Click(sender As Object, e As EventArgs) Handles btnScore.Click
If i < scores.Length Then
'display inputbox to the user
runs = InputBox("Enter score for " & (i + 1) & " innings", "Score")
'if runs is entered
If runs <> "" Then
'parse the value of runs
If (Double.TryParse(runs, out)) Then
'parse the runs and add it to the array scores()
scores(i) = Double.Parse(runs)
runningScore += scores(i)
'add the rainfall value to the listbox along with month name
lstScores.Items.Add(scores(i) & " :" & runningScore)
'increment the value of i
i = i + 1
Else
'display error message
MessageBox.Show(VALID_MESSAGE)
lblTotal.Text = ""
End If
Else
'if runs is empty then display error message
MessageBox.Show("Enter runs for " & i & "innings")
End If
Else
MessageBox.Show(ONLY_MESSAGE)
End If
If runs < 0 Then
MessageBox.Show(VALID_MESSAGE)
End If
'calculate total runs And display on the lable
If scores(6) = 7 Then
lblTotal.Text = String.Format("final score is {0}", scores.Sum())
End If
End Sub
'Clear Menu click
Private Sub ClearToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles mnuClear.Click
lstScores.Items.Clear()
lblTotal.Text = ""
'reset i to 0
i = 0
End Sub
'Exit Menu click
Private Sub ExitToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles mnuExit.Click
'close application
Application.Exit()
End Sub
End Class
I would really appreciate it if you could help. Thank you.

Answer 1

Private Sub btnScore_Click(sender As Object, e As EventArgs) Handles btnScore.Click
If i < scores.Length Then
'display inputbox to the user
runs = InputBox("Enter score for " & (i + 1) & " innings", "Score")
'if runs is entered
If runs < 0 Then
MessageBox.Show(VALID_MESSAGE)
Exit Sub
ElseIf runs <> "" Then
'parse the value of runs
If (Double.TryParse(runs, out)) Then
'parse the runs and add it to the array scores()
scores(i) = Double.Parse(runs)
runningScore += scores(i)
'add the rainfall value to the listbox along with month name
lstScores.Items.Add(scores(i) & " :" & runningScore)
'increment the value of i
i = i + 1
Else
'display error message
MessageBox.Show(VALID_MESSAGE)
lblTotal.Text = ""
End If
Else
'if runs is empty then display error message
MessageBox.Show("Enter runs for " & i & "innings")
End If
Else
MessageBox.Show(ONLY_MESSAGE)
End If
If runs < 0 Then
MessageBox.Show(VALID_MESSAGE)
End If
'calculate total runs And display on the lable
If scores(6) = 7 Then
lblTotal.Text = String.Format("final score is {0}", scores.Sum())
End If
End Sub
This is the reason why if you input invalid data it will add into lstScores, because your If statement.. is in bottom of your code, although is not recommend where you put the If else statement... Remember reading of the code is start in top to bottom.
Your first If statement is like this. If runs <> "" then ...., of course if you type the -1 value in the Input Text the Boolean will result to true, If -1 <> "" = true, then it will proceed to the statement which is
If (Double.TryParse(runs, out)) Then
'parse the runs and add it to the array scores()
scores(i) = Double.Parse(runs)
runningScore += scores(i)
'add the rainfall value to the listbox along with month name
lstScores.Items.Add(scores(i) & " :" & runningScore)
'increment the value of i
i = i + 1
This is the line of code even the value is invalid or not it still adding value in the lstScores, lstScores.Items.Add(scores(i) & " :" & runningScore)
Now after that statement you will receive a message which is :
Enter valid runs value
If runs < 0 Then
MessageBox.Show(VALID_MESSAGE)
End If
That code is the reason why you receiving the message. If you input -1 of course the result of boolean is true, why? -1 is lessthan to 0 which is true.
The thing i do is, I've insert If statement.. above, which is If runs < 0 then .... and also Exit Sub to instantly end the statement. If you input -1 to Input Text the result is something like this, if runs(-1) lessthan to 0 the Boolean result is true then it will proceed to statement which is the Message and Exit Sub.
Try my code above, and also use Breakpoints.. Hope this helps..