SRL Archive - C#/Visual Basic Help and Tutorials

i'm starting visual basics, and i'm trying to make a simple calculator. so far i have

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim Num1, Num2, Answer As Integer
        Dim OP As String

        Num1 = TextBox1.Text
        Op = TextBox4.Text
        Num2 = TextBox2.Text
        Answer = TextBox3.Text

        If Op = "+" Then
            Answer = Num1 + Num2
        ElseIf Op = "-" Then
            Answer = Num1 - Num2
        ElseIf OP = "*" Then
            Answer = Num1 * Num2
        ElseIf OP = "/" Then
            Answer = Num1 / Num2
        ElseIf OP = "^" Then
            Answer = Num1 ^ Num2
        End If




    End Sub
End Class

and i get the error: Conversion from string "Answer" to type 'Integer' is not valid.

what do i do to convert it properly?

I dunno if it'll work, but try this:

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim Num1, Num2, Answer As Integer
        Dim OP As String

        Num1 = TextBox1.Text
        Op = TextBox4.Text
        Num2 = TextBox2.Text
        Answer = TextBox3.Text

        If Op = "+" Then
            Answer = Str(Num1 + Num2)
        ElseIf Op = "-" Then
            Answer = Str(Num1 - Num2)
        ElseIf OP = "*" Then
            Answer = Str(Num1 * Num2)
        ElseIf OP = "/" Then
            Answer = Str(Num1 / Num2)
        ElseIf OP = "^" Then
            Answer = Str(Num1 ^ Num2)
        End If




    End Sub
End Class

From: senrath
I dunno if it'll work, but try this:

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim Num1, Num2, Answer As Integer
        Dim OP As String

        Num1 = TextBox1.Text
        Op = TextBox4.Text
        Num2 = TextBox2.Text
        Answer = TextBox3.Text

        If Op = "+" Then
            Answer = Str(Num1 + Num2)
        ElseIf Op = "-" Then
            Answer = Str(Num1 - Num2)
        ElseIf OP = "*" Then
            Answer = Str(Num1 * Num2)
        ElseIf OP = "/" Then
            Answer = Str(Num1 / Num2)
        ElseIf OP = "^" Then
            Answer = Str(Num1 ^ Num2)
        End If




    End Sub
End Class

nope, didnt work =\ thanks though

I'm an idiot. I misread the code. This should work:

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim Num1, Num2, Answer As Integer
        Dim OP As String

        Num1 = Val(TextBox1.Text)
        Op = TextBox4.Text
        Num2 = Val(TextBox2.Text)
        Answer = Val(TextBox3.Text)

        If Op = "+" Then
            Answer = Num1 + Num2
        ElseIf Op = "-" Then
            Answer = Num1 - Num2
        ElseIf OP = "*" Then
            Answer = Num1 * Num2
        ElseIf OP = "/" Then
            Answer = Num1 / Num2
        ElseIf OP = "^" Then
            Answer = Num1 ^ Num2
        End If




    End Sub
End Class

instead of:

        If Op = "+" Then
            Answer = Num1 + Num2
        ElseIf Op = "-" Then
            Answer = Num1 - Num2
        ElseIf OP = "*" Then
            Answer = Num1 * Num2
        ElseIf OP = "/" Then
            Answer = Num1 / Num2
        ElseIf OP = "^" Then
            Answer = Num1 ^ Num2
        End If

do:

      select case op
case is "+"
answer = num1+num2
case is "-"
answer = num1-num2
case is "*"
answer = num1*num2
case is "/"
answer = num1/num2
case is "^"
answer = num1^num2
end select

here is a source from a school project I did last semester:

Public Class Form1

    Dim operand1 As Double = 0
    Dim operand2 As Double = 0
    Dim op As String = Nothing
    Dim newOperand As Boolean = True

    'Updates the calculator display
    '
    'pre: Global variable newOperand is True when the current display should be changed to a 
    'new number and False when the current display should be updated with a new digit.
    'The Tag property of the button clicked contains the number corresponding to the 
    'number on the button.
    'post: The calculator display has been updated to show a new number or an
    'additional digit.
    '
    Private Sub Number_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles _
    btnDot.Click, btn0.Click, btn1.Click, btn2.Click, btn3.Click, btn4.Click, btn5.Click, _
    btn6.Click, btn7.Click, btn8.Click, btn9.Click
        Dim btnNumberClicked As Button = sender
        If newOperand Then
            Me.txtDisplay.Text = btnNumberClicked.Tag
            newOperand = False
        Else
            Me.txtDisplay.Text &= btnNumberClicked.Tag
        End If
    End Sub

    'Clears the calculator display
    '
    'post: The calculator display has been changed to 0 and the global variables 
    'have been reinitialized.
    '
    Private Sub btnClear_Click(ByVal sender As Object, ByVal e As System.EventArgs) _
    Handles btnClear.Click
        Me.txtDisplay.Text = "0"
        operand1 = 0
        operand2 = 0
        newOperand = True
        op = Nothing
    End Sub

    'Ends the applications
    '
    'post: The application is ended
    '
    Private Sub btnOff_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnOff.Click
        Application.Exit()
    End Sub

    'Updates the value of the operands and updates the calculator display to show the result of a 
    'calculation if two operands have been entered
    '
    'post: The calculator display has been changed to show the result of a calculation if a second 
    'operator had been clicked, otherwise the display has not been changed.
    '
    Private Sub btnOperator_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnPlus.Click, _
    btnMinus.Click, btnTimes.Click, btnDivide.Click, btnEqual.Click
        Dim operatorSelected As Button = sender

        'No operator previously clicked or a calculation just performed
        If (operand1 = 0 And op = Nothing) Or op = "=" Then
            operand1 = Val(Me.txtDisplay.Text)
        Else    'second operand entered and a second operator clicked
            operand2 = Val(Me.txtDisplay.Text)
            operand1 = Calculate(operand1, operand2, op)
            Me.txtDisplay.Text = operand1
        End If

        'Store operator for use when the next operator is clicked
        op = operatorSelected.Tag
        newOperand = True
    End Sub

    'Performs a calculation using two operands and an operator
    '
    'post: The result of a calculation has been returned
    '
    Function Calculate(ByVal firstOperand As Double, ByVal secondOperand As Double, _
    ByVal op As String) As Double
        Select Case op
            Case "+"
                Return (firstOperand + secondOperand)
            Case "-"
                Return (firstOperand - secondOperand)
            Case "x"
                Return (firstOperand * secondOperand)
            Case "/"
                Return (firstOperand / secondOperand)
        End Select
    End Function
End Class

This should work. I don't have VB on this computer, so I can't tell you exactly. You set Answer as an integer, when all you have to do is set it to a string and convert it. You should also do a select case like bballer said, because each "if" makes a process run and so you're making 5 process run which equals memory hog which equals inefficient code.

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim Num1, Num2 As Integer
        Dim OP, Answer As String

        Num1 = TextBox1.Text
        Op = TextBox4.Text
        Num2 = TextBox2.Text
        Answer = TextBox3.Text

        select case Op
          case is "+"
            Answer = CStr(Num1 + Num2)
          case is "-"
            Answer = CStr(Num1 - Num2)
          case is "*"
            Answer = CStr(Num1 * Num2)
          case is "/"
            Answer = CStr(Num1 / Num2)
          case is "^"
            Answer = CStr(Num1 ^ Num2)
        end select

    End Sub
End Class

Let me know if it works.

~Camo