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A little help from Reflection...

Today a friend of mine asked me how to define enums containing white spaces, after my initial response (”Why the *** you want to do that?”) i ended up with this code that demonstrates how 'flexible' is .NET (in this case using VB but, as you know, language is just a detail...)

Created a custom attribute...

<AttributeUsage(AttributeTargets.Field)> _
Public NotInheritable Class EnumDisplay : Inherits Attribute
Private mText As String
Public Sub New(ByVal text As String)
 mText = text
End Sub
 Public ReadOnly Property Text() As String
 Get
   Return mText
 End Get
 End Property
End Class

...and a simple helper function that uses both Generics and Reflection...

Public Class EnumHelper
  Public Shared Function EnumToString(Of T As Structure)(ByVal value As T) As String
  Dim sourceEnum As Type = value.GetType()
  Dim name As String = [Enum].GetName(sourceEnum, value)
  Dim fi As FieldInfo = sourceEnum.GetField(name)
  Dim att As EnumDisplay = TryCast(Attribute.GetCustomAttribute(fi, GetType(EnumDisplay)), EnumDisplay)
  If (att IsNot Nothing) Then Return att.Text
  Return name
  End Function
End Class

Now you can define your own Enum and decorate it with EnumDisplay where needed...

Public Enum TempState
 Low
 Middle
 <EnumDisplay("Hi Temperature")> HiTemperature
 TooHigh
End Enum

And get a string representation of enum field using:

Console.WriteLine(EnumHelper.EnumToString(TempState.HiTemperature)) ' Hi Temperature

Cool!

posted on giovedì 9 febbraio 2006 00:47 Print

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