Math functions in VB

I have two questions:

I'm aware that Math.Min() will only accept two values, but I need to get the minimum value from the contents of ten textboxes; so, is there a Math function that will allow me to do this or is there a better way to do it?

Also, how do I get round the problem of showing the minimum value as zero if any of the textboxes contain zeros or blanks?

Hope you can help.

You can put your values into an array or list and then use the Enumerable.Min extension method, e.g.

vb.net Code:

Dim textBoxes = Me.Controls.OfType(Of TextBox)()
Dim numbers = textboxes.Where(Function(tb) Integer.TryParse(tb.Text, Nothing)).Select(Function(tb) Integer.Parse(tb.Text))
Dim minNumber = numbers.Min()

Thanks but I'm still unsure. The textboxes from which I need to extract the minimum number are tbAAH, tbCol, tbDE, tbLex and tbUni; so where do I fit these into your code?

Instead of
Dim textBoxes = Me.Controls.OfType(Of TextBox)()

Try
Dim textBoxes() as TextBox = {tbAAH, tbCol, tbDE, tbLex, tbUni}

Thanks. I now have the following:
CODE
Dim textBoxes() As TextBox = {tbAAH, tbCol, tbDE, tbLex, tbUni}
Dim numbers = textBoxes.Where(Function(tb) Integer.TryParse(tb.Text, Nothing)).Select(Function(tb) Integer.Parse(tb.Text))
Dim minNumber = numbers.Min()
CODE
I get the following message:
An unhandled exception of type 'System.InvalidOperationException' occurred in System.Core.dll
Additional information: Sequence contains no elements
So presumably something needs to be put in the brackets after Dim minNumber = numbers.Min(); but what should be in there?

Quote:

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Originally Posted by Pianoman23

Thanks. I now have the following:
CODE
Dim textBoxes() As TextBox = {tbAAH, tbCol, tbDE, tbLex, tbUni}
Dim numbers = textBoxes.Where(Function(tb) Integer.TryParse(tb.Text, Nothing)).Select(Function(tb) Integer.Parse(tb.Text))
Dim minNumber = numbers.Min()
CODE
I get the following message:
An unhandled exception of type 'System.InvalidOperationException' occurred in System.Core.dll
Additional information: Sequence contains no elements
So presumably something needs to be put in the brackets after Dim minNumber = numbers.Min(); but what should be in there?

---

You would get that error if none of the textboxes can be parsed as a number, because the numbers collection would be empty. You could prevent the exception by checking the numbers count, e.g.

Code:

---

If numbers.Count > 0 Then
        Dim minNumber = numbers.Min()
      Else
        MessageBox.Show("no minimum number")
      End If

---

but maybe the lambda expression could be improved to allow for this situation.

BB

I really don't know what I'm doing here. I'm now up to the following code but still getting errors

Code:
Dim textBoxes() As TextBox = {tbAAH, tbCol, tbDE, tbLex, tbUni}
Dim numbers = textBoxes.Where(Function(tb) Integer.TryParse(tb.Text, Nothing)).Select(Function(tb) Integer.Parse(tb.Text))
Dim minNumber = numbers.Min()
If numbers.Count > 0 Then
Dim minNumber = numbers.Min()
Else
MessageBox.Show("no minimum number")
End If
MsgBox(minNumber)
Code

You can't write MsgBox(minNumber) because in your present code minNumber isn't declared outside the If block. I wrote it that way to avoid letting minNumber=0 if all your textboxes are empty; instead you get a message.

Here's an alternative way of writing the code which I hope you'll find easier to understand.

Code:

---

      Dim textBoxes() As TextBox = {tbAAH, tbCol, tbDE, tbLex, tbUni} 'make an array of your textboxes
      Dim numbers As New List(Of Integer)
      Dim minNumber As Integer
      For Each tb As TextBox In textBoxes
        Dim n As Integer
        If Integer.TryParse(tb.Text, n) Then
            numbers.Add(n) 'if the textbox contains a number, add it to the list
        End If
      Next
      If numbers.Count > 0 Then
        'at least one textbox contains number
        minNumber = numbers.Min
        MessageBox.Show(minNumber.ToString)
      Else
        'none of the text boxes contains a number
        minNumber = Integer.MinValue
        MessageBox.Show("no numbers found in text boxes")
      End If

---

This time minNumber gets the value of Integer.MinValue (something less than - 2 billion) instead of 0 when none of the textboxes contains a number. It has to have some value, but the idea is that you just ignore it.

By the way, please enclose your code in tags with square brackets like this: [code] ... [/code]. Or select a block of code in the forum message editor and hit the # button.

BB

Thanks. I'll remember the tip about displaying code.

I've inputted the code. I'm not getting any error messages but even though tbAAH contains 14.67 and tbCol contains 14.07 (the others are empty) the messagebox says "no numbers found in text boxes".

That's because everyone assumed the numbers would be integers. Just change Integer to Double everywhere it occurs in the above code.

BB

Quote:

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Originally Posted by boops boops

That's because everyone assumed the numbers would be integers.

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I didn't assume that. I just provided an example in which the numbers would be Integers. Unfortunately, too many people think that an example is something that you can copy and paste and expect to work as is, rather than a demonstration of a principle that you then supposed to implement in the code you write yourself. If you don't read and understand an example then you shouldn't be surprised if it doesn't work in your specific case. Too much copy and paste and not enough read and think.

Apologies for my ignorance.

Quote:

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Originally Posted by jmcilhinney

something that you can copy and paste and expect to work as is, rather than a demonstration of a principle that you then supposed to implement in the code you write yourself. If you don't read and understand an example then you shouldn't be surprised if it doesn't work in your specific case. Too much copy and paste and not enough read and think.

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Read my singnature

Quote:

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Disclaimer: When code is given for example - it is merely a example.

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Add this to your singature so people know ahead a time its merely for example

A another useful tip is when putting code in your posts use the [code][/code] Brackets or hit the VB button on the toolbar.