One if statement for multiple controls? - vb.net

Question

I would like to know if you can use one general if statement for the same condition but on multiple controls?
for example, If I have five labels and I want each label to say "hello" when I push a button I would write something like
If Label1.Text = "" Then
Label1.Text = "hello"
End If
But instead of writing an if statement for each label is there a way to apply this one if statement to all five labels?

Answer 1

Yes, you can iterate over all controls in a form, but you'd need to restrict them to Label instances, fortunately LINQ makes this easy:
Dim emptyLabels As IEnumerable(Of Label) = _
Me.Controls.OfType(Of Label)().Where(Function(l) l.Text.Length = 0)
For Each label As Label In emptyLabels
label.Text = "hello"
Next

Answer 2

You could do this:
Dim ifEmptyAssignHello As Action(Of Label) = _
Sub(l)
If l.Text = "" Then
l.Text = "Hello"
End If
End Sub
ifEmptyAssignHello(Label1)
ifEmptyAssignHello(Label2)
ifEmptyAssignHello(Label3)

Answer 3

Well you could
make a method which takes a label,
then pass labels into it.
Public Sub SayHello(l As Label)
If (l is Nothing) Then Return
If (l.Text = "") Then
l.Text = "Hello"
End If
End Sub
...
For Each l As Label in anyLabels
SayHello(l)
End For

Answer 4

The most concise way to do what you describe is to iterate over an explicit array of the labels. VB.Net will notice that they're all Labels and figure out the type for you.
For Each individualLabel In {Label1,
Label2,
Label3,
Label4,
Label5}
If individualLabel.Text = "" Then individualLabel.Text = "hello"
Next
Of course, if you need to do this more than once, you'll want to define a variable to refer to that particular group of five labels.
Dim myFiveLabels As IEnumerable(Of Label) = {Label1, Label2, Label3, Label4, Label5}
(We explicitly define the variable as an IEnumerable because this way it can only be used to iterate over each element of the group. If it were defined as an Array or List, you could e.g. add / remove elements and generally complicate its behaviour.)