Enum Type?

[JDYoder]

Not sure what this would be called, but in VB.Net, is it possible to have some type of enum that is string based?

 

For example, I'm tracking DataType in my program for some objects, which can be "Integer", "String", "Boolean", etc. I'd like to declare variable "X" of type "DataTypeFields". Then when I type "X = ", the intellisense will list all possible string items declared within "DataTypeFields".

 

I can do this if "DataTypeFields" is an enum, but that has to be numeric. And in my case, doing that would be worthless, arbitrary, and a pain to convert from string to integer, and back when needed, just to get the intellisense to work. Any ideas?

[PlausiblyDamp]

Although enums are of an integer type (byte, int16, int32 etc.) they can easily be converted to and from a string representation.

 

You can always convert to the string representation by using the .ToString method and click gives a short sample of how to go the other way.

Edited March 2, 2007 by PlausiblyDamp

[JDYoder]

That's what I'm doing now with a couple of functions, but I'm finding it to be somewhat of a pain to always have to remember when to call which. Not only between saving and displaying, but when I need to compare values at different points in the program, meaning I always have to make sure I'm either comparing integer to integer or string to string, depending on where I'm at.

 

I had hoped VB.Net allowed for string-type enums so I could avoid this minor headache, but I guess not. Thanks for confirming my suspicions.

[IngisKahn]

It sounds like you may be better served by using a hash table.

[PlausiblyDamp]

Not entirely sure where your problem lies - any chance you could post some code to give a better idea what you are doing?

[Robby]

A cheap way of getting string representation is to use a structure. Setup your Const String types and whatever they equal to in the struct.

[JDYoder]

>> It sounds like you may be better served by using a hash table.

 

Don't now what this is, but I'm willing to look into it if you can tell me why and point me in the right direction.

 

 

 

>> A cheap way of getting string representation is to use a structure. Setup your Const String types and whatever they equal to in the struct.

 

Meaning I need to remember to type the structure name everytime, followed by "." at which point intellisense will pop them up? I thought about doing that with a class, but it still means a new programmer would have to know to reference that class (or structure) every time. Whereas now, by having all my vars declared as an enum, intellisense pop up just by hitting "=". However, it's still something to reconsider, assuming I'm understanding you.

 

 

 

>> Not entirely sure where your problem lies - any chance you could post some code to give a better idea what you are doing?

 

It's not so much a problem as it is a hassle. But if you're curious, I'm querying SQL Server via a stored proc that's returning some of our own defined types. So we not only have "Integer", "Date", etc, but "Amount", "Percent", "Rate", etc. I have to track these with every control on my report designer in the Tag field. So I have this...

 

 

Public Enum RWFieldTypes
   ' Assign values rather than start with understood 0 since that equals nothing, which we don't
   '   want to be true. (Otherwise comparing to nothing would be the same as the first element.)
   DateField = 1
   IntegerField = 2
   DecimalField = 3
   BooleanField = 4
   TextField = 5
   AmountField = 6
   PercentField = 7
   RateField = 8
End Enum


Public Function RWFieldTypeToString(ByVal vFieldType As RWFieldTypes) As String
   Return Replace(vFieldType.ToString(), "Field", "")
End Function


Public Function RWFieldType(ByVal strFieldType As String) As RWFieldTypes
   Try
       Return System.Enum.Parse(GetType(RWFieldTypes), strFieldType & "Field")
   Catch ex As Exception
       Return 0
   End Try
End Function

 

 

So when I want to store "Amount" in a Tag field, I need to call RWFieldTypeToString to convert AmountField to "Amount." (And there are a few reasons we don't store the number value in the Tag field, which I'll not bore you with.) Likewise, if I need to compare a field's type, I call RWFieldType to convert it back to a number so intellisense works, rather than have to rely on typing "Percent" (or whatever) throughout the code.

 

So I don't like having to call these two global functions throughout my code, but I think it's what I have to do unless another solution comes along. So that's my "dilemma." Nothing major. Just annoying and not very elegant to my way of thinking.

[mskeel]

You could put all of that data into it's own class. That would prevent the global aspect of the two methods. So the class would consist of the enum and the two methods. At leas then everything would be in one place and not sprinkled about...

[JDYoder]

But then I'd just have to declare a global variable of that type, which would essentially be the same thing. Seems like six of one and half dozen of the other.

[mskeel]

You could declere the varialbe private and use accessor methods (properties) which would insulate the rest of your code from a type change. Then if you decided to impliment this using a hashtable in the future you would only change this class and you wouldn't have to change any of your other code. Right now if you started using a hashtable as someone suggested you might have to change more than just those two methods.

 

It was just a thought. It may not be the most appropriate decision to make for your code and it does seem like, for all intents and purposes, it would be nearly equivelant. The only advantage would be additional information hiding, which it seems you have bought through the use of the enum, so it probably won't matter.

[IngisKahn]

Too bad you're not using C#. If you were then you could put this in a class and define implicit type conversion operators.

[JDYoder]

>> Too bad you're not using C#. If you were then you could put this in a class and define implicit type conversion operators.

 

I've dabbled in C#, so I'm curious to know what exactly this is. Or is it really complicated to get into?

[IngisKahn]

Basically you just make 2 functions for converting your class to/from a string so you could use your class just like it was a string.