New to Visual Basic, need help with code

[Mattshu]

Hi. I'm new to the VB language but I'm familiar with programming/scripting.

I'm also new to these forums so please forgive me if this post is in the wrong board.

I started playing with Visual Basic when I realized my tech school had it installed on the network computers, and became a bit addicted (within a few days) of the possibilities it contains.

I've started writing something basic.. a number guessing game in a Windows Application. The layout may not be optimal/strategically formed, because I'm not familiar with the language yet.

Here's the code:

Public Class Form1
 
    Public Rand As Integer = 0
    Public Attempts As Integer = 5
 
    Public Function DoFail()
        MsgBox("You failed. The number was: " + Rand)
        Attempts = 0
        Return 1
    End Function
 
    Private Sub Button1_Click() Handles Button1.Click
        If Rand < 1 Then
            Randomize()
            Rand = Int(Rnd() * 11)
            If Rand = 0 Then
                Rand += 1
            End If
        End If
        If GuessBox.Text = 0 Then
            MsgBox("You must enter a guess!", MsgBoxStyle.Exclamation, "Guess")
        Else
            Dim Guess As Integer = GuessBox.Text
            If Guess > Rand Then
                Attempts -= 1
                If Attempts = 0 Then
                    DoFail()
                End If
                StatusStrip1.Text = "Remaining attempts: " + Attempts
                OutputBox.Text = "Lower!"
            End If
            If Guess < Rand Then
                Attempts -= 1
                If Attempts = 0 Then
                    DoFail()
                End If
                StatusStrip1.Text = "Remaining attempts: " + Attempts
                OutputBox.Text = "Higher!"
            End If
            If Guess = Rand Then
                StatusStrip1.Text = "Winner!"
                MsgBox("You've got it! The number was: " + Rand, MsgBoxStyle.Information, "Winner!")
                Me.Close()
            End If
        End If
    End Sub
End Class

When I attempt to run this, the dialog opens fine. Until I click the "Guess" (Button1) button, which sort of freezes the dialog, returning me to the Visual Basic editor debugger. If the guessed number matches the random number (or if its lower or higher) then it returns the related code (involving the integers 'Rand' and 'Guess'):

If Guess > Rand:

StatusStrip1.Text = "Remaining attempts: " + Attempts
 
'This line is highlighted with this message:
'Conversion from string "Remaining attempts: " to type 'Double' is not valid.

If Guess < Rand:
(same as above)

If Guess = Rand:

MsgBox("You've got it! The number was: " + Rand, MsgBoxStyle.Information, "Winner!")
 
'This line is highlighted with this message:
'Conversion from string "You've got it! The number was: " to type 'Double' is not valid.

What am I doing wrong?

Thanks in advanced.

[VBFnewcomer]

Welcome to the vbforums
pls specify what version of VB you are working with.
Happy programming

[si_the_geek]

Thread moved from 'VB6 and Earlier' forum to 'VB.Net' (VB2002 and later) forum

(for the benefit of others, Mattshu's profile says VB2008 Express)

[mendhak]

Have you stepped through the code? You can place breakpoints at lines of code (F9) and when the line hits, the debugger will bring it up, usually with a yellow highlight. You can then press move your mouse over variables to look at the values, and F10 and F11 to step to the next line to see the flow of execution.

Welcome to the forums.

[Sorn2008]

Yeh like Mendhak said Place a BP (Breakpoint) on the following line...

Private Sub Button1_Click() Handles Button1.Click

Not sure if it matters to much but my OnClick Sub begins like this.

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

And Hit F5 to run in Debug mode, and then Click the button it should now stop on the BP, then simply hit F8 to step through each line of code.

[Shaggy Hiker]

A couple other points that aren't quite related to the problem directly:

1) Get rid of Randomize and rnd, look at the Random object. Those other randomizers were used in VB6 and earlier, and are decidedly inferior to the Random object for ease of use. For instance, with the Random object you no longer need the call to Randomize. Also, to get a value between Min and Max using the random object you would do something like this:

Dim rn as New Random

rn.GetNext(Min, Max+1)

The Max+1 is because GetNext includes the lower bound (Min), but not the upper bound (Max), so Max+1 will include Max.

2) Turn Option Strict ON. By default, Option Strict is set to Off, a default decision that is truly unfortunate. You will probably get a fair number of errors when you turn Option Strict ON, such as this line:

Dim Guess As Integer = GuessBox.Text

Since GuessBox.Text returns a String and you are putting it into an Integer variable. Without Option Strict ON, this works ok, because the compiler does the conversion for you. You would need to change that to either:

Dim Guess As Integer = CInt(GuessBox.Text)


or a safer conversion using TryParse. Either way looks like more typing, and it is, but you will avoid some especially subtle bugs, and the code will run faster. Those implicit conversions that you create with Option Strict OFF are not all that fast. Therefore, you get safer, faster, code with Option Strict ON for the cost of slightly more typing. That's a very good trade-off.

[Runesmith]

If Guess > Rand:

StatusStrip1.Text = "Remaining attempts: " + Attempts
 
'This line is highlighted with this message:
'Conversion from string "Remaining attempts: " to type 'Double' is not valid.

If Guess < Rand:
(same as above)

If Guess = Rand:

MsgBox("You've got it! The number was: " + Rand, MsgBoxStyle.Information, "Winner!")
 
'This line is highlighted with this message:
'Conversion from string "You've got it! The number was: " to type 'Double' is not valid.

What am I doing wrong?

Thanks in advanced.

You are using "+" to concatenate strings, which is not valid in VB.NET. Try "&" operator instead. Go to the Visual Studio help, and search "string concatenation" for further information.

Also, I suggest using .ToString to convert the numeric values to string, instead of doing an implicit conversion. Eg. "The number was " & rand.ToString

[MaximilianMayrhofer]

CInt vs Int32.Parse, I wonder which is more appropriate. I would lean towards Parse because it is specifically geared towards strings.

[Shaggy Hiker]

The + concatenator works ok in .NET, however, with Option Strict Off, there is a chance that you will not get what you want. That's a rare issue, though.

CInt and Int32.Parse will both throw exceptions if the string being converted is not a valid integer.

[Runesmith]

Both errors that Mattshu highlighted in his code were caused by using the "+" operator. The compiler tries to convert the first operand (a string in this case) to Double, and throws the exception.

[Shaggy Hiker]

That's bizarre. One item is a string, the result is being put into a string, yet it is the string that is being converted to a number. I just checked it in 2005, and it's true.

The real problem, though, is that Option Strict is OFF. That line wouldn't even compile with Option Strict ON, because the error would have been caught right from the start. The + operator does concatenate strings, but it also adds numbers. Without the implicit conversions required by Option Strict, the compiler didn't know whether to convert the string to a double, or the number to a string, and it guessed wrong. I'm surprised at that, since the string was a literal, rather than a variable, but the result is the same: Option Strict should be ON in all cases except the very rare times when it HAS to be off. Aside from catching problems like this, your code will run faster, too.

[dbasnett]

a crude solution

Option Strict On : Option Explicit On
Public Class Form1
    Dim number2Guess As Integer
    Dim r As New Random
    Const maxGuess As Integer = 5
    Dim guesses As Integer
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Button1.Text = "Guess"
        Me.AcceptButton = Button1
        StartGame()
    End Sub
    Private Sub StartGame()
        ToolStripStatusLabel1.Text = "Type your Guess, then press enter or click Guess"
        number2Guess = r.Next(1, 11) 'a number between 1 and 10 inclusive
        guesses = 0
        ToolStripStatusLabel2.Text = "Guesses Left " & maxGuess.ToString
        TextBox1.Text = ""
        TextBox1.Select()
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim guessed As Integer = -1
        Integer.TryParse(TextBox1.Text, guessed)
        If guessed = number2Guess Then
            'winner
            MessageBox.Show("You Guessed It")
            StartGame()
            Exit Sub
        Else
            guesses += 1
            If guesses >= maxGuess Then
                MessageBox.Show("The Number was " & number2Guess.ToString()) 'show number
                StartGame()
                Exit Sub
            Else
                ToolStripStatusLabel2.Text = "Guesses Left " & (maxGuess - guesses).ToString
            End If
        End If
        TextBox1.Select()
        TextBox1.SelectAll()
    End Sub
End Class