The ever occuring problem of how to implement a String Enum or a Constant in an elegant way is an annoyance for all programmers. No programmer likes hardcoding constants or enums but they are often necessary. Below is another way to accomplish this.
Imports System.ComponentModel
Imports MyPatterns.TypeCodes
Imports MyPatterns.CategoryCodes
Public Enum TypeCodes
<Description("Type A")> TypeA = 0
<Description("Type B")> TypeB
<Description("Type C")> TypeC
End Enum
Public Enum CategoryCodes
<Description("General")> General = 0
<Description("Specific")> Specific
<Description("Other")> Other
End Enum
Public NotInheritable Class Constants
#Region "Resources"
Private Shared myTypes As Dictionary(Of TypeCodes, ConstantItem) = Nothing
Public Shared ReadOnly Property Types() As Dictionary(Of TypeCodes, ConstantItem)
Get
If myTypes Is Nothing Then
myTypes = New Dictionary(Of TypeCodes, ConstantItem)
BuildTypes(myTypes)
End If
Return myTypes
End Get
End Property
Private Shared Sub BuildTypes(ByRef dict As Dictionary(Of TypeCodes, ConstantItem))
With dict
.Add(TypeCodes.TypeA, New ConstantItem(TypeCodes.TypeA.Description, "Type A are..."))
.Add(TypeCodes.TypeB, New ConstantItem(TypeCodes.TypeB.Description, "Type B are..."))
.Add(TypeCodes.TypeC, New ConstantItem(TypeCodes.TypeC.Description, "Type C are..."))
End With
End Sub
#End Region
#Region "Categories"
Private Shared myCategories As Dictionary(Of CategoryCodes, ConstantItem) = Nothing
Public Shared ReadOnly Property Categories() As Dictionary(Of CategoryCodes, ConstantItem)
Get
If myCategories Is Nothing Then
myCategories = New Dictionary(Of CategoryCodes, ConstantItem)
BuildCategories(myCategories)
End If
Return myCategories
End Get
End Property
Private Shared Sub BuildCategories(ByRef dict As Dictionary(Of CategoryCodes, ConstantItem))
With dict
.Add(CategoryCodes.General, New ConstantItem(CategoryCodes.General.Description, "General category"))
.Add(CategoryCodes.Specific, New ConstantItem(CategoryCodes.Specific.Description, "Specific category"))
.Add(CategoryCodes.Other, New ConstantItem(CategoryCodes.Other.Description, "Other category"))
End With
End Sub
#End Region
End Class
Public NotInheritable Class ConstantItem
#Region "Constructors"
''' <summary>
''' Default constructor.
''' </summary>
Public Sub New()
'Do nothing
End Sub
''' <summary>
''' Simple constructor.
''' </summary>
Sub New(value As String)
Me.Name = value
Me.Description = value
End Sub
''' <summary>
''' Proper constructor.
''' </summary>
Sub New(name As String, description As String)
Me.Name = name
Me.Description = description
End Sub
#End Region
Property Name As String
Property Description As String
''' <summary>
''' See http://stackoverflow.com/questions/293215/default-properties-in-vb-net
''' </summary>
Public Shared Widening Operator CType(value As String) As ConstantItem
Return New ConstantItem(value)
End Operator
''' <summary>
''' See http://stackoverflow.com/questions/293215/default-properties-in-vb-net
''' </summary>
Public Shared Widening Operator CType(value As ConstantItem) As String
Return value.Name
End Operator
End Class
Public Class ConstantsExample
Public Sub UseConstant()
Dim value As String = Constants.Types(TypeA)
Dim category As String = Constants.Categories(General)
End Sub
End Class