vb.net combine and or operators

Question

very simple question, how to combine and or operators into the same statement.

c.GetType is getType(TextBox) AND foo or bar or baz

this is not working

For Each c As Control In Me.Controls
    If (c.GetType Is GetType(TextBox)) And ((c.Name <> "txtID") Or (c.Name <> "txtAltEmail")) Then
        'do something
    End If
Next

this works:

For Each c As Control In Me.Controls
    If (c.GetType Is GetType(TextBox)) And (c.Name <> "txtID") Then
        'do something
    End If
Next

thanks, I'm a .net newbie!

What error are you getting? the first statment looks fine to me — Luis, Jul 11 '12 at 22:03
@LuisSánchez: The first statement is equivalent to `If (c.GetType Is GetType(TextBox)) And True Then`. — Heinzi, Jul 11 '12 at 22:14
@Heinzi Indeed, for a moment there I was seeing and `=` instead of a `<>` — Luis, Jul 11 '12 at 22:23

score 2 · Accepted Answer · edited May 23 '17 at 12:20

By the way, you can use LINQ which improves the intelligibility.:

Dim allTextBoxes = From txt In Me.Controls.OfType(Of TextBox)()
                  Where txt.Name <> "txtID" AndAlso txt.Name <> "txtAltEmail"
For Each txt In allTextBoxes
    ' do something with the TextBox '
Next

OfType returns only the controls of the given type, in this case TextBoxes
Where filters the controls by the Name property (note: And and AndAlso difference)
the For Each iterates the resulting IEnumerable(Of TextBox)

Heinzi · Answer 2 · 2012-07-11T22:12:58.743

Your first statement does not make sense from a mathematical point of view. The expression

X <> A or X <> B

will always return true (given that A <> B, which is satisfied in your case since "txtID" <> "txtAltEmail").

(If X = A, the second clause will be true. If X = B, the first clause will be true. If X is anything else, both clauses will be true.)

What you probably meant to write was

If (TypeOf c Is TextBox) AndAlso (c.Name <> "txtID") AndAlso (c.Name <> "txtAltEmail") Then

or

If (TypeOf c Is TextBox) AndAlso Not ((c.Name = "txtID") OrElse (c.Name = "txtAltEmail")) Then

which is logically equivalent.

(I've also taken the liberty to change your type check to a more elegant variant and replace And/Or with their more efficient counterparts.)

@LuisSánchez: Thanks. I've decided to remove the `)` instead. — Heinzi, Jul 11 '12 at 22:15

vb.net combine and or operators

2 Answers2