Most Efficient Way To Write This Loop VB.Net - vb.net

Question

Good afternoon all, I am beginning my first forays into programming and have decided to begin with VB.net as I can get VS2010 professional free through MS Dreamspark program.
I have been following some basic tutorials online and am now writing a small program that runs a loop to add all the numbers together between two numbers input by the user.
Below is the code I have written:
Public Class Form1
Private Sub cmdAddNumbers_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdAddNumbers.Click
Dim NumberOne As Integer
Dim NumberTwo As Integer
Dim Result As Integer
Dim i As Integer
If Not IsNumeric(txtNumberOne.Text) Then
MsgBox("Please Enter A Valid Number For Number One")
txtNumberOne.Clear()
Exit Sub
ElseIf txtNumberOne.Text = 0 Then
MsgBox("Please Enter A Valid Number For Number One")
txtNumberOne.Clear()
Exit Sub
ElseIf txtNumberOne.Text > 0 And IsNumeric(txtNumberOne.Text) Then
NumberOne = txtNumberOne.Text
End If
If Not IsNumeric(txtNumberTwo.Text) Then
MsgBox("Please Enter A Valid Number For Number Two")
txtNumberTwo.Clear()
Exit Sub
ElseIf txtNumberTwo.Text < NumberOne Then
MsgBox("Please Enter A Valid Number For Number Two")
txtNumberTwo.Clear()
Exit Sub
ElseIf txtNumberTwo.Text > NumberOne And IsNumeric(txtNumberTwo.Text) Then
NumberTwo = txtNumberTwo.Text
End If
For i = NumberOne To NumberTwo
Result = Result + i
Next i
txtResult.Text = Result
txtNumberOne.Clear()
txtNumberTwo.Clear()
End Sub
End Class
Now, I am wondering if I have written the most efficent If statements to execute this code or if they can be written any simpler with AND/OR statements to possibly remove some of the ElseIf's.
Any insight is greatly appreciated.
Thank you,
Alex

Answer 1

You should start with putting Option Strict On at the top of your code to force yourself to write code without implicit conversions between strings and numbers. An example of a pitfall in your code is where you compare the string value txtNumberTwo.Text to the numeric value NumberOne; it isn't obvious if the string is converted to a number so that the comparison works properly, or if the number is converted to a string so that it does a string comparison instead.
You can use the Int32.TryParse method to parse each number only once instead of three times:
Dim numberOne As Integer
Dim numberTwo As Integer
Dim result As Integer
If Not Int32.TryParse(txtNumberOne.Text, numberOne) Then
MsgBox("Please Enter A Valid Number For Number One")
txtNumberOne.Clear()
Exit Sub
ElseIf numberOne <= 0 Then
MsgBox("Please Enter A Valid Number For Number One")
txtNumberOne.Clear()
Exit Sub
End If
If Not Int32.TryParse(txtNumberTwo.Text, numberTwo) Then
MsgBox("Please Enter A Valid Number For Number Two")
txtNumberTwo.Clear()
Exit Sub
ElseIf numberTwo < numberOne Then
MsgBox("Please Enter A Valid Number For Number Two")
txtNumberTwo.Clear()
Exit Sub
End If
Your loop is not needed at all. You can calculate the sum directly:
Result = (numberOne + numberTwo) * (numberTwo + 1 - numberOne) / 2

Answer 2

What about:
If Not IsNumeric(txtNumberOne.Text) Or txtNumberOne.Text <= 0 Then
MsgBox("Please Enter A Valid Number For Number One")
txtNumberOne.Clear()
Exit Sub
Else
NumberOne = txtNumberOne.Text
End If
If Not IsNumeric(txtNumberTwo.Text) Or txtNumberTwo.Text < NumberOne Then
MsgBox("Please Enter A Valid Number For Number Two")
txtNumberTwo.Clear()
Exit Sub
Else
NumberTwo = txtNumberTwo.Text
End If
Be aware that if NumberOne is equal to Textbox2.Text, NumberTwo is never assigned

Answer 3

i think the best solution for you is just set the textboxes to be able to accept only numbers, that way you can avoid all the checks if the texts is numeric or not and only check if its bigger than zero.
to set the textboxes to accept only numbers copy this function:
Private Function TrapKey(ByVal KCode As String) As Boolean
If (KCode >= 48 And KCode <= 57) Or KCode = 8 Then
TrapKey = False
Else
TrapKey = True
End If
End Function
and in the keypress event of the textboxes add
e.Handled = TrapKey(Asc(e.KeyChar))

Answer 4

If Not IsNumeric(txtNumberOne.Text) Then
MsgBox("Please Enter A Valid Number For Number One")
txtNumberOne.Clear()
Exit Sub
ElseIf txtNumberOne.Text = 0 Then
MsgBox("Please Enter A Valid Number For Number One")
txtNumberOne.Clear()
Exit Sub
ElseIf txtNumberOne.Text > 0 And IsNumeric(txtNumberOne.Text) Then
NumberOne = txtNumberOne.Text
End If
The third If is superflious. We know it must be IsNumeric, as it passed the first If, and we know it cannot be 0, as it passed the second If. (You also make no allowances at all, if it happens to be negative)
Now, it been a while since I last did VB.Net, but I'm pretty sure it still have a distinct between strings & integers, which means txtNumberOne.Text = 0 shouldn't even compile.
And also, why are you making your users guess what a "valid number" is?
Dim numberOne as Integer
If IsNumeric(txtNumberOne.Text) Then
numberOne = CInt(txtNumberOne.Text)
else
numberOne = -1;
End If
If numberOne < 1
MsgBox("Please Enter A Positive Number For Number One")
txtNumberOne.Clear()
Exit Sub
End If

Answer 5

Dim doub As Double
If Not (Double.TryParse(txtNumberOne.Text, doub) AndAlso doub > 0) Then
MsgBox("Please Enter A Valid Number For Number One")
txtNumberOne.Clear()
Else
NumberOne = doub
End If
If Not (Double.TryParse(txtNumberTwo.Text, doub) AndAlso doub > 0) Then
MsgBox("Please Enter A Valid Number For Number Two")
txtNumberTwo.Clear()
Else
NumberTwo = doub
End If
I think this is waht you are looking for
Result = (NumberTwo * (NumberTwo + 1) / 2) - ((NumberOne - 1) * (NumberOne) / 2)