if statement problems
 

I'm having problems with if statements
present value (PV) should be no larger than $10000
interest rate is not higher than 10 and no less than 2
and number of years at least 3

I've tried the if statements with error messageboxs but I was getting confused with all the if's and the messagebox didn't show up right. The following code is my code before entering the if's. Any insight would be very helpful, thank you.

Public Class Form1



    Public Function FV(ByVal PV As Object, ByVal i As Object, ByVal n As Object) As Object

        'Formula to calculate Future Value(FV)

        'PV denotes Present Value

        FV = PV * (1 + i / 100) ^ n



    End Function



    Private Sub compute_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles compute.Click

        'This procedure will calculate Future Value

        Dim FutureVal As Decimal

        Dim PresentVal As Decimal

        Dim interest As Object

        Dim period As Object



        PresentVal = PV.Text

        interest = rate.Text

        period = years.Text

        FutureVal = FV(PresentVal, interest, period)

        lblFV.Text = FormatCurrency(FutureVal)



    End Sub





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

        Me.Close()

    End Sub





End Class

Re: if statement problems
 

I'm assuming you want to check the values before making the call to the FV function. If that's the case, you could accomplish what you're trying to do with three simple if statements. Something like the following would probably work just fine:

Private Sub compute_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles compute.Click

'This procedure will calculate Future Value

Dim FutureVal As Decimal

Dim PresentVal As Decimal

Dim interest As Object

Dim period As Object

PresentVal = PV.Text

interest = rate.Text

period = years.Text



If CDbl(PresentVal) > 10000.00 Then

MessageBox.Show("Present Value must not be larger than 10000")

End Sub

End If

If CDbl(interest) < 2 Or CDbl(interest) > 10 Then

MessageBox.Show("Interest Rate must be between 2 and 10")

End Sub

End If

If CInt(period) < 3 Then

MessageBox.Show("The Period must be at least 3 years")

End Sub

End If



FutureVal = FV(PresentVal, interest, period)

lblFV.Text = FormatCurrency(FutureVal)

End Sub

If you just need something simple, this should work. You may want to change the conversions depending on what you're assuming will be input from the text fields, and you would obviously want to use some kind of exception handling anytime you're converting the text from user input into various data types.

Re: if statement problems
 

The way I should implement is : using the LostFocus event for the textboxes. After the lostfocus you can warn a user corresponding the maximum or minimum values needed. Second is creating yourself a class in which you calculate the FV.

code below:

Public Class Class1

    Private _FutureValue As Decimal

    Private _PresentVal As Decimal

    Private _Interest As Double

    Private _Period As Integer

   'just for remembering the formula (for me :=) )

    Private Const CN_Formula As String = "FV = PV * (1 + i / 100) ^ n"



    Public Property FutureValue() As Decimal

        Get

            Return _FutureValue

        End Get

        Set(ByVal value As Decimal)

            _FutureValue = value

        End Set

    End Property

    Public Property PresentVal() As Decimal

        Get

            Return _PresentVal

        End Get

        Set(ByVal value As Decimal)

            _PresentVal = value

        End Set

    End Property

    Public Property Interest() As Double

        Get

            Return _Interest

        End Get

        Set(ByVal value As Double)

            _Interest = value

        End Set

    End Property

    Public Property Period() As Integer

        Get

            Return _Period

        End Get

        Set(ByVal value As Integer)

            _Period = value

        End Set

    End Property

    Public Function Calculate() As Decimal

        Try

            Return Me.PresentVal * (1 + Me.Interest / 100) ^ Me.Period

        Catch ex As Exception

            Throw New ArgumentException("For some reason no calculation could be done!")

        End Try



    End Function



    Public Sub New()

        MyBase.New()

    End Sub

End Class

formcode:

Public Class Form1

    Private myCalc As Class1 = New Class1

    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged

        Try

            myCalc.PresentVal = CType(DirectCast(sender, TextBox).Text, Decimal)

        Catch ex As Exception

            MsgBox(ex.Message)

        End Try

    End Sub





    Private Sub TextBox2_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox2.TextChanged

        Try

            myCalc.Period = CType(DirectCast(sender, TextBox).Text, Double)

        Catch ex As Exception

            MsgBox(ex.Message)

        End Try

    End Sub



    Private Sub TextBox3_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox3.TextChanged

        Try

            myCalc.Interest = CType(DirectCast(sender, TextBox).Text, Integer)

        Catch ex As Exception

            MsgBox(ex.Message)

        End Try

    End Sub



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

        Try

            Me.TextBox4.Text = myCalc.Calculate

        Catch ex As Exception

            MsgBox(ex.Message)

        End Try



    End Sub

End Class

Re: if statement problems
 

thanks it worked bcasp, much appreciated !!