CODEWITHSUNDEEP
vb.netloops
user3516803
user3516803

Reputation:

How do I end a Do...Until loop

I am making a program at school and I don't know how to end the Do...Until loop. What I have already is a program that when a button is clicked an input box comes up asking for a password. What I then want to happen is if the user enters the wrong password, the price that appears should double and they get prompted for the password again. If they get the password correct, i want the program to exit. This is what I have already:

Public Class Form1

    Private Property userPassword As String

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim price = 100
        Dim realPassword = "hello"
        Do
            Dim userPassword = InputBox("Please enter the correct password to claim your money", "Claim Winnings")
            If userPassword = realPassword Then
                MsgBox("You owe us £" & price)
            Else
                MsgBox("Incorrect password entered. You now owe £" & price * 2)

            End If
        Loop Until userPassword = realPassword
    End Sub

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    End Sub

End Class

The price doesn't go up if they enter the wrong password.

Upvotes: 1

Views: 1985

Answers (2)

GoroundoVipa
GoroundoVipa

Reputation: 259

Use While userPassword <> realPassword

the while statement will wait until userPassword and realPassword is equal, if equal the while statement will terminate.

Upvotes: 0

Olivier Jacot-Descombes
Olivier Jacot-Descombes

Reputation: 112352

The problem is that you have a property as well as a variable called userPassword.

Since the variable is defined inside of the loop with ...

Dim userPassword = InputBox(...)

... the property will never be set and the variable's scope will be limited to the loop block (the statements inside the loop). Therefore the loop condition Loop Until userPassword = realPassword refers to the property that has never been set!

Fix: Remove the Dim

userPassword = InputBox(...) 'Now this sets the property
                             'instead of declaring a new variable

And also change the value of price

price = 2 * price

or

price *= 2

You are only showing the double price, but the variable price is never changed!

It is usage in VB to start the property names with an upper case letter and the local variables and the method parameter names with a lower case letter. This helps to avoid confusion.

Note: The scope of a variable, i.e. the area where it is known to VB, is the statement block where it has been declared

Dim k, x, y As Integer

IF x = y Then
    Dim i As Integer = 5
Else
    k = i ' Not possible since `i` is not known here!
End If

If you want to leave a loop from within the loop, you can use Exit Do. If you want to leave the method altogether, you can do it with Return. But there is no need to use it in your solution. I'm only mentioning it, because it was a subject of discussion in the comments.

Do
    DoSomething()
    If WeWantToExitNow Then
        Exit Do    ' Or "Return" if you want to leave the method here.
    End If
    DoSomethingElse()
Loop Until x = y

Upvotes: 2

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