Passing arguments to methods in VB - vb.net

Question

I'm hoping you guys can help with a problem that should be simple to solve, I've just had issues finding a solution. In the program that I'm writing some of the textbox's have to be numeric between 1 and 10, and others just have to be numeric. Instead of coding each textbox to verify these parameters I decided to write methods for each of them. I'm having problems passing the arguments and getting it to function correctly. Included is some of my code that shows what I'm trying to accomplish.
Public Shared Sub checkforonetoten(ByVal onetoten As Double)
If (onetoten > 1 & onetoten < 10) Then
Else
MessageBox.Show("Please enter a Number between 1-10", "Error")
End If
End Sub
Public Shared Sub checkfornumber(numCheck As Double)
Dim numericCheck As Boolean
numericCheck = IsNumeric(numCheck)
If (numericCheck = False) Then
MessageBox.Show("Please enter a number", "Error")
End If
End Sub
Private Sub textboxS_TextChanged(sender As Object, e As EventArgs) Handles textboxS.TextChanged
Dim S As Double
S = textboxS.Text
checkfornumber(S)
checkforonetoten(S)
End Sub

Answer 1

One of your main problems is you're converting your text without validating it. You're also programming without the Options On to warn you of bad conversion techniques like you're using in the event handler.
The TryParse method would come in handy here:
Private Sub textboxS_TextChanged(sender As Object, e As EventArgs) Handles textboxS.TextChanged
Dim S As Double
If Double.TryParse(textboxS.Text, S) Then
checkforonetoten(S)
End If
End Sub
Since the TryParse method validates your text and sets the value to 'S', you only need to check the range.
Of course using NumericUpDown controls would make all this moot, since the values will always only be numbers and you can set the range on each one.

Answer 2

one way to structure it is to have one event procedure process the similar TB types:
Private Sub textboxS_TextChanged(sender As Object, e As EventArgs) _
Handles textbox1.TextChanged, textbox12.TextChanged, _
Handles textbox16.TextChanged
Dim S As Double
If Double.TryParse(Ctype(sender, TextBox).Text, S) Then
' or place the Check code here for all the TextBoxes listed above
checkforonetoten(S)
End If
End Sub
The plain numeric kind:
Private Sub textboxQ_TextChanged(sender As Object, e As EventArgs) _
Handles textbox2.TextChanged, textbox6.TextChanged
Dim S As Double
If Double.TryParse(Ctype(sender, TextBox).Text, S) = False Then
MessageBox.Show("Please enter a number", "Error")
End If
End Sub
Rather than calling a function and passing the current TextBox from events (which is fine), have 2 or 3 events process them all. The point is adding/moving the Handles clause to a common event procedure (be sure to delete the old ones).
If you do decide to call a common function, dont do anything in the events (you still have one per TB) and do it all in the common proc:
Private Sub textboxS_TextChanged(sender As Object, e As EventArgs) _
Handles textboxS.TextChanged
checkforonetoten(Sender)
End Sub
private Sub checkforonetoten(tb As Textbox)
Dim S As Double
If Double.TryParse(tb.Text, S) Then
' your check for 1 - 10 on var S
else
' error: not a valid number
End If
end sub
Also:
If (onetoten > 1 & onetoten < 10) Then
should be:
If (onetoten > 1) AndAlso (onetoten < 10) Then