Container for Constants in VB.NET

Question

VB.NET (.NET 2)

Say I have some constants that depends one of other, and I decided to keep them together in a container instead of keeping it as individual constants in a class.

I thought use a Structure for that scope, but compiler force me to declare a private member for that structure.

  ' Compile error: at least one private member is needed '
  Private Structure BandSizes 
    Const BandHeight As Short = HourHeight + 20
    Const HourHeight As Short = HalfHourHeight + 20
    Const HalfHourHeight As Short = LineHeight + PictureHeight + 20
    Const PictureHeight As Short = 20
    Const LineHeight As Short = StopHeight + 10
    Const LineWidth As Short = 50
    Const StopHeight As Short = 30
  End Structure

As I have only a few integer constants, should I create a shared (static) class?

Answer 1

An enum might be a better option. Not sure about VB syntax, but C# would be:

internal enum BandSizes {
  BandHeight = HourHeight + 20,
  HourHeight = HalfHourHeight + 20,
  HalfHourHeight = LineHeight + PictureHeight + 20,
  PictureHeight = 20,
  LineHeight = StopHeight + 10,
  LineWidth = 50,
  StopHeight = 30,
}

(NB. if this is an namespace scope, internal is the most restrictive access, but private is possible if a member of a class or structure.)

EDIT: Here's the VB version:

Friend Enum BandSizes
    BandHeight = HourHeight + 20
    HourHeight = HalfHourHeight + 20
    HalfHourHeight = LineHeight + PictureHeight + 20
    PictureHeight = 20
    LineHeight = StopHeight + 10
    LineWidth = 50
    StopHeight = 30
End Enum

Where Friend is the VB for internal (and the same limitation on Private is only possible for type members).

Answer 2

Since it's VB.Net, if they are truly global constants and their name by themself is enough you can also create a Module to keep them in.

Also, be aware that if these constants are accessed from external assemblies there can be issues if the values of these constants can ever change. So if these were public and put in a class library for example it might be better to have them as ReadOnly rather than constant.

Answer 3

In my opinion the best Option for this purpose is to create a (private) class with only shared/static members/constants. You dont need to create an Object and you can control accessibility as you want.

   Private NotInheritable Class BandSizes
        Public Const BandHeight As Short = HourHeight + 20
        Public Const HourHeight As Short = HalfHourHeight + 20
        Public Const HalfHourHeight As Short = LineHeight + PictureHeight + 20
        Public Const PictureHeight As Short = 20
        Public Const LineHeight As Short = StopHeight + 10
        Public Const LineWidth As Short = 50
        Public Const StopHeight As Short = 30

        Private Sub New()
        End Sub
    End Class

EDIT: added NotInheritable to the class because it is what the compiler would produce as IL when you use a Module. I prefer a "standard-Dot.Net"-way over the VB-only stuff. Besides you have more control over its accessibility and you can make it as innerclass. This is in fact the VB.Net pendant to a C# static class.