Below are two examples of handlers for the ADD button.
(The first example is not modularized; the second example is)
Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles btnAdd.Click
'''' Sum the two numbers.
'''' DECLARATIONS:
Dim first As Double
Dim second As Double
Dim answer As Double
'''' INPUT ''''
first = Val(Me.txtFirst.Text) ' Convert string to #
second = Val(Me.txtSecond.Text)
'''' PROCESSING ''''
answer = first + second ' Add numbers
'''' OUTPUT ''''
Dim s As String
Dim t As String
s = "The sum is "
t = Format(answer) ' Convert # to string
Me.lstAnswers.Items.Add(s + t)
End Sub
The second code example is fully "modularized" to simplify its "re-use" for other buttons.
Private Sub btnAdd_Click( ..., ... ) Handles btnAdd.Click
'''' Input two numbers, process them, produce labelled output.
Dim first as Integer = getFirst() '''' INPUT ''''
Dim second as Integer = getSecond()
Dim s as String
'''' PROCESSING ''''
answer = calcAdd( first, second )
s= "The sum is "
'****** FOR RE-USE, CHANGE THE ABOVE TWO LINES
'****** (AND WRITE A NEW calc FUNCTION).
call saywhat ( s, answer ) '''' OUTPUT ''''
End Sub
Function calcaAdd( a as Integer, b as Integer) as Integer
'''' Add the two numbers.
Dim result as Integer
result= a + b
return result
End Function
'======= INPUT METHODS ========'
Function getFirst() as Integer
'''' Get the first input; convert to integer value. ''''
return Val(Me.txtFirst.Text) ' Convert string to #
End Function
Function getSecond() as Integer
'''' Get the 2nd input; convert to integer value. ''''
return Val(Me.txtSecond.Text) ' Convert string to #
End Function
'======= OUTPUT METHODS ========'
Sub getFirst( msg as string, v as integer )
'''' Display a message followed by a value.
Me.lstAnswers.Items.Add( msg + Format(v) )
End Sub