[TUT] Basic Calculator [VB]

[RaZoR03]

I leeched this from here!

Follow these simple steps and create your own calculator

first start off by creating a standard .exe application project

and create two text boxes, one Combo box, one command button and one label.

name them like this:
text box 1: txtNumber1
text box 2: txtNumber2
comdo box: cmbOperator
command button: cmdCalculate
label: lblResult

now go into your coding view and start off by adding

Option Explicit
to the code
the option explicit prevent variables and such from being created without proper deceleration and it makes debugging bigger applications much easier and the reason for adding it here is because its best to get used to add it to every project from the start

now we need to add the desired operator\'s to the combo box:
we want the population of the combo box to happen while the application loads and how we do this is simple

write the code

Private Sub Form_Load()

End Sub


into your code
any code we now add between those two lines will be executed doing the load of the form
Note: The Form part of the Form_load is the name of the form

now we add the code to populate the combo
write the code:

cmdOperator.AddItem (\"+\")
cmdOperator.AddItem (\"-\")
cmdOperator.AddItem (\"*\")
cmdOperator.AddItem (\"/\")


between the other lines we added before.

Now we need to add the code to calculate the numbers with the chosen Operator.

add the code:

Private Sub cmdCalculate_Click()

End Sub

below all the code we have written

all code we add between those lines will be executed then the user press the cmdCalculate Button

the code for calculating this is fairly simple and easy to under stand

we want to calculate the two numbers with the chosen operator and we want to display a error message if the user haven\'t chosen anything

we will do this by a if else statement
add the code:

If cmdOperator.Text = \"\" Then

Else

End If


between the last lines we wrote

now we checks if the user haven\'t chosen anything and do a specific code if he haven\'t otherwise it will execute the \"Else\" code

now we want to display a message box and we do this with a \"msgbox\" function:

add the code:

MsgBox (\"You most chose a operator!!\")


right after

If cmdOperator.Text = \"\" Then


this will display a standard message box to the user

now that we have checked if the user has chosen anything we need to add the calculation code:

now after the else line we need to have one way to know what operator the user has chosen

this is done by a select case statement (it can also be done by a if statement but the case statement is much cleaner

now add the code:


Select Case cmbOperator.Text
Case \"+\"

Case \"-\"

Case \"*\"

Case \"/\"

End Select


right after the \"Else\" Line

this will allow us to add code for every operator

now we will take the case \"+\" together and then you can try the other ones by yourself(just to learn) if you don\'t want to do this then just download the attachment for the complete source

we want to display the result in the label (lblResult)
and we do this by using the property .Caption

so now we start building up the line of code

first in the line add

lblResult.Caption
and we want to sett this property to the result of the calculation this is done by a \"=\" operator so add the \"=\" right after the last part of the code now we need to use the \"Val()\" Function to make the application treat the numbers as numbers otherwise they will be treated as text

so the next code is just Val(txtNumber1.Text) [operator here] Val(txtNumber2.Text)

example:

lblResult.Caption = Val(txtNumber1.Text) + Val(txtNumber2.Text)