Most efficient way to validate multiple textboxes against a tolerance value

Question

I have a series of text boxes in a table to gather input as below:

enter image description here

The user will input a target and actual value for each measurement point they require. I would then like to validate the actual values against the target values based upon the tolerance inputted in the tolerance textbox. The tolerance will be the same for all measurement points inputted, however the user will not always input all 10 measurement points.

I have also created a very basic class containing a function that accepts the target, actual and tolerance values then returns a Boolean depending on whether the actual value is within tolerance. I realise I could use this with a ruck load of if statements to check each textbox for input then use the class to perform the validation, however this seems like a lot of code repetition and a bit crude. My question being is there a better way I can perform this validation?

Class content

Public Class TolerenceHelper
Public Function IsInTolerence(ByVal target As Integer, ByVal actual As Integer, ByVal tolerence As Integer) As Boolean
 Dim upper As Integer = target + tolerence
 Dim lower As Integer = target - tolerence
 If actual < lower OrElse actual > upper Then
 Return False
 Else
 Return True
 End If
End Function

Calling the function as below:

Dim m1 As TolerenceHelper
Dim flag As Boolean = True
m1 = New TolerenceHelper
If m1.IsInTolerence(Integer.Parse(txtT1.Text), Integer.Parse(txtA1.Text), Integer.Parse(txtTolerance.Text)) = False Then
 flag = False
End If
If flag = False Then
 lblTest.Text = "Out of tolerance"
Else
 lblTest.Text = "In tolerance"
End If

• Daniel: Do you have a separate lblTest for each check, or are you reusing the same field? Are you only checking 1 at a time?
• Mathieu Guindon: Isn't it spelled "tolerance"?
• Malachi: Jimsan, has anyone appropriately answered your question? if not please provide some specifics on what more you would like
• Jimsan: Malachi, I didn't mark an answer as everyone has valid points. I ended up using the code that I added in the edit of my post. Thank you all for your help though
• Malachi: @Jimsan if you chose that as a solution you should post it as an answer and accept it as the answer

Answer 1

I would write it like this

Dim m1 As TolerenceHelper
Dim flag As Boolean = True
m1 = New TolerenceHelper
flag = m1.IsInTolerence(Integer.Parse(txtT1.Text), Integer.Parse(txtA1.Text), Integer.Parse(txtTolerance.Text))
If flag = False Then
 lblTest.Text = "Out of tolerance"
Else
 lblTest.Text = "In tolerance"
End If

that function returns a boolean so you can just assign it the flag or you could do it like this and avoid creating the flag boolean as well

Dim m1 As TolerenceHelper
m1 = New TolerenceHelper
If m1.IsInTolerence(Integer.Parse(txtT1.Text), Integer.Parse(txtA1.Text), Integer.Parse(txtTolerance.Text)) Then
 lblTest.Text = "In tolerance"
Else
 lblTest.Text = "Out of tolerance"
End If

---

In your Function IsInTolerence you could eliminate some variables by writing it like this:

Public Function IsInTolerence(ByVal target As Integer, ByVal actual As Integer, ByVal tolerence As Integer) As Boolean
 If (target - tolerence <= actual AND actual =< target + tolerence)
 Return True
 Else
 Return False
 End If
End Function

Straight to the point.

check if it is true first, and then dump out in all other cases, this would cover a null or something else.

---

Remove Code Duplication with a list of TextBox Objects

I am thinking that you create a list of the text boxes, then you should be able to loop through that list, checking each text box for the following.

1. if it has a value entered
2. if the tolerance is met
3. some kind of highlighting to show that the tolerance was not met.

I am not sure on the syntax, but this would be a good way to do it, because you would only have to type out the logic once and then loop through the list of TextBoxes, and it would be more maintainable because you could just add TextBoxes any time you like and it shouldn't affect the any of the other code.

dim TextBoxListActual as New List(Of TextBox)
TextBoxListActual.Add(txtT1)
TextBoxListActual.Add(txtT2)
TextBoxListActual.Add(txtT3)
Dim TextBoxListTarget as New List(Of TextBox)
TextBoxListTarget.Add(txtA1)
TextBoxListTarget.Add(txtA2)
TextBoxListTarget.Add(txtA3)
dim m1 As TolerenceHelper
m1 = New TolerenceHelper
For index As Integer = 0 To TextBoxListActual.Count
 If m1.IsInTolerence(Integer.Parse(TextBoxListTarget(index).value), Integer.Parse(TextBoxListActual(index).value), Integer.Parse(txtTolerance.Text))
 lblTest.Text = "In Tolerance"
 Else
 lblTest.Text = "Out of Tolerance"
 End If
Next

little bit of an example. probably not perfect.

• Daniel: I'd definitely do the 2nd revision, or the first revision but change If flag = False to simply If flag and then change the true clause to being first.

Answer 2

Instead of performing each test via a series of if statements or needing to add your textboxes to a list, you can perform a simple for loop and utilize the FindControl command of the page.

This would allow you to write code something like this:

For i As Integer = 1 To 10
 Dim TargetBox As TextBox = Me.FindControl("txtT" & i)
 Dim ActualBox As TextBox = Me.FindControl("txtA" & i)
 If IsNothing(TargetBox) OrElse IsNothing(ActualBox) Then
 'Couldn't find TextBox so just try the next number
 Continue For
 Else
 If TolerenceHelper.IsInTolerence(Integer.Parse(TargetBox.Text), Integer.Parse(ActualBox.Text), Tolerence) Then
 lblText.Text += String.Format("Trial {0} In tolerance",i)
 Else
 lblText.Text += String.Format("Trial {0} Out of Tolerence",i)
 End If
 End If
Next

• Malachi: if they change the amount of Textboxes they would have to change the for loop. with the List of Text boxes the code won't change all they would have to do is in the declaration, another textboxList.add(textbox43) or they could find a better way of doing it like that. there has to be a collection collection or something where you could select all the textboxes in said group or something, this doesn't seem maintainable.

Answer 3

As written, there is no reason for IsInTolerence not to be a shared function because TolerenceHelper has no benefit to actually being instantiated.

To make it shared, you would instead declare it like so:

Public Shared Function IsInTolerence(...

This will give you the advantage of having your initial calls instead of being:

Dim m1 As TolerenceHelper
m1 = New TolerenceHelper
If m1.IsInTolerence(...

You would use:

If TolerenceHelper.IsInTolerence(...

Answer 4

Instead of parsing the tolerence each time, you'd want to set it to a variable or possibly make a property. I like the property method simply because it allows for a lot of flexibility.

Here's an example:

Protected Property Tolerence As Integer
 Get
 Static _Tolerence As Integer = -1 'Static variable so Tolerence parsed only once per postback
 If _Tolerence = -1 AndAlso Not Integer.TryParse(txtTolerence.Text, _Tolerence) Then
 _Tolerence = 0 ' or your default value or whatever you like
 End If
 Return _Tolerence
 End Get
 Set(value As Integer)
 txtTolerence.Text = value
 End Set
End Property

You may note that I used this Property in one of my other answers.

Answer 5

You could shorten IsInTolerence to being a 1-liner like this:

Function IsInTolerence(ByVal target As Integer, ByVal actual As Integer, ByVal tolerence As Integer) As Boolean
 Return target - tolerence <= actual And actual <= target + tolerence
End Function

A micro optimization note... I'd initially used AndAlso in my comment, but that runs slower even if the first check is always false.