Using select case program to calculate addition subtraction in VB.NET

Question

1.00/5 (1 vote)

See more:

Hi All,
I am New to Vb,please guide me how to get the result of addition and subtraction using case in vb.net.
Thanks in Advance

What I have tried:

VB.NET

Public Class Form1

    Public Function Calculator(ByVal strMod As String)
        Dim Num1 As Integer = TextBox1.Text
        Dim Num2 As Integer = TextBox2.Text
        Dim Num3 As Single = TextBox3.Text
        Select Case strMod
            Case Calculator("Add")
                Num3 = Num1 + Num2
            Case Calculator("Sub")
                Num3 = Num1 - Num2
        End Select
        Return Num3
    End Function

    Public Sub Output_Click(sender As Object, e As EventArgs) Handles Button1.Click

        Dim result As Integer = Calculator("Sub")
        MessageBox.Show(Convert.ToString(result), "Result")
    End Sub

    Public Sub Clear_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Me.Close()
    End Sub
End Class

Posted 25-Sep-16 8:21am

Member 12605293

Updated 10-May-18 21:10pm

Wendelius

v3

Add a Solution

Comments

[no name] 25-Sep-16 14:32pm

What, exactly, is it that you think "Case Calculator("Add")" is supposed to do?

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Maciej Los · Accepted Answer · 2016-09-25T11:47:00

Well, in my opinion you're doing it wrong way.

As to the body of function...
From programming practice perspective, function should be as much universal as possible. So, it can take zero, one or more parameters, but it shouldn't refer to the controls on the form!

VB.NET

Public Function Calculator(ByVal strMod As String)
    Dim Num1 As Integer = TextBox1.Text
    Dim Num2 As Integer = TextBox2.Text
    Dim Num3 As Single = TextBox3.Text
    Select Case strMod
        Case Calculator("Add")
            Num3 = Num1 + Num2
        Case Calculator("Sub")
            Num3 = Num1 - Num2
    End Select
    Return Num3
End Function

Your function should use 3 parameters:

a number, which stores actual result (zero by default)
a number, which is used for further calculation
a sign [+], [-], [*] or [/] - aka mathematical operator

VB.NET

Public Function Calculate(ByVal totalValue As Single, ByVal currentValue As Single, ByVal mathOperator As String)
    Dim retVal as Single = 0

    'here your logic
    Select Case mathOperator
        Case "+"
            retVal = totalValue + currentValue 
        Case "-"  
            retVal = totalValue - currentValue 
        Case "*"
            retVal = totalValue * currentValue 
        Case "/"  
            retVal = totalValue / currentValue 
    End Select
 
    Return retVal
End Function

Usage:
Let's say, you have one button for addition operation [+], one for subtraction operation [-], etc, but all buttons refer to the same Click event (see: How to: Connect Multiple Events to a Single Event Handler in Windows Forms[^])

VB.NET

Private Sub ButtonAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonAdd.Click, ButtonSub.Click, ...
Dim tot As Single = Convert.ToSingle(Me.TextBoxResult.Text)
Dim cur As Single  = Convert.ToSingle(Me.TextBoxValue.Text) 
Dim moper As String = TryCast(sender, Button).Text '
TextBoxResult.Text = Calculate(tot, cur, moper)
End Sub

As you can see, i used Convert.ToSingle()[^] method to convert string into single.

Here is MSDN example: Windows VB.Net Calculator sample in VB.NET for Visual Studio 2008[^]

But, finally, you need mathematical expression evaluator/parser. See:
Simple Math Parser - Home[^]
Fast Lightweight Expression Evaluator - Home[^]
ILCalc: Arithmetical Expressions Evaluator - Home[^]
NCalc - Mathematical Expressions Evaluator for .NET - Home[^]
The expression evaluator revisited (Eval function in 100% managed .NET)[^]
A Calculation Engine for .NET[^]

Wendelius · Accepted Answer · 2016-09-25T08:36:00

There are few things you have missed
- The function should have a return type
- Instead of checking the parameter you call the Calculator function recursively in the case structure

Try something like the following

VB.NET

Public Function Calculator(ByVal strMod As String) As Single
    Dim Num1 As Integer = TextBox1.Text
    Dim Num2 As Integer = TextBox2.Text
    Dim Num3 As Single = TextBox3.Text

    Select Case strMod
        Case "Add"
            Num3 = Num1 + Num2
        Case "Sub"
            Num3 = Num1 - Num2
    End Select
    Return Num3
End Function

Also note:
- not sure why you assign a value to num3 from the textbox3. Should you do it the other way around if Textbox3 is for the result
- Instead of passing a string for the operation I'd suggest using enumeration. See Enum Statement (Visual Basic)[^]
- and it would probably be more elegant if you would pass num1 and num2 as parameters to the function. This way the function wouldn't depend on the user interface objects and could be used for different kinds of objects and situations.

[ADDED]
For assigning the value to TextBox3

VB.NET

Public Sub Output_Click(sender As Object, e As EventArgs) Handles Button1.Click
    TextBox3.Text = Calculator("Sub")
End Sub

Also get familiar with debugging the program. For example go through Navigating through Code with the Debugger[^]

Using select case program to calculate addition subtraction in VB.NET

2 solutions

Solution 2

Solution 1

Add your solution here

Preview 0