Optional Object parameter passing in a function

Question

Hi,

I have this code. I want to use the same procedure with the controls on a form instead of just controls on a groupbox. The catch is i do not want to repeat the procedure. I tried to declare grpbox as optional but it will ask for the default value and I don't know what i can give as default.
Any other recommendations to make this function precise would also be welcomed.

Thanks

Public Sub checkCriteria(ByVal GrpBox As GroupBox)

Dim grp As GroupBox = CType(GrpBox, GroupBox)

Dim ctrl As Control

Dim flag As Boolean

flag = False

For Each ctrl In grp.Controls

If TypeOf ctrl Is TextBox Then

Dim sctrl As TextBox = CType(ctrl, TextBox)

Try

If sctrl.Text <= txtasUMin Or sctrl.Text >= txtasUMax Then

sctrl.BackColor = Color.OrangeRed

sctrl.ReadOnly = False

flag = True

End If

Catch e As InvalidCastException

sctrl.BackColor = Color.OrangeRed

sctrl.ReadOnly = False

flag = True

End Try

End If

Next

If flag = True Then

MsgBox(txtMsg, MsgBoxStyle.Critical, "Message centre")

Else

settxtasUMin()

MsgBox("Data validation completed")

End If

End Sub

Answer 1

Optional GrpBox As GroupBox = Nothing

 

Or you can also do an overload where the procedure accepts any container object...or an overload for each type of container you would like to work with

 

HTH

Answer 2

Hi,

The Nothing value is declaring but how should i check the value nothing in the If statement?
i don't really understand how can i do overload. Can you elaborate on this point plz.

Thanks

Answer 3

If IsNothing(grpbox) then

...DoSomething

End If

 

Examples of Overloading:

Public Sub checkCriteria(ByVal GrpBox As GroupBox)

Dim ctrl As Control

Dim flag As Boolean

flag = False

For Each ctrl In GrpBox.Controls

********

Public Sub checkCriteria(ByVal frm As Form)

Dim ctrl As Control

Dim flag As Boolean

flag = False

For Each ctrl In frm.Controls

*******

Public Sub checkCriteria(ByVal pnl As Panel)

Dim ctrl As Control

Dim flag As Boolean

flag = False

For Each ctrl In pnl.Controls

 

*******

Public Sub checkCriteria(ByVal Obj As Object)

If TypeOf Obj Is GroupBox Then

Dim grpbox As GroupBox = CType(Obj, GroupBox)

End If

If TypeOf Obj Is Panel Then

Dim pnl As Panel = CType(Obj, Panel)

End If

...

End Sub

 

Answer 4

Thanks Dman1, really appreciate it.