Enums ?? Database ??

Question

I have a simple question but one that has confused me for sometime now. I'll use a simple sample here to explain my problem. Lets say I have a simple database which as 3 tables in it. Users, Roles, UserRoles. I will assume that everyone can see the relationship between these tables. In my c# code I have the way to add a new user also to the db. I also have methods within my code which allow the user to create new roles. When I add a new user I would like to expose a enumeration of userroles. public int AddUser(string userName, UserRoles role) //example method to add user My question is a how can I keep my enumeration sync'd with my database roles? I would think that there should be a way to do this but the only thing that I can think of is dynamically creating the enumeration. But when I think about this, how would that work. I give someone my class to user, when they do a myobject obj = new myobject(); how to i get the enumerations at that time. Hope I have supplied enough information for someone to help me out on this problem. Any help or input on this problem would be greatly appreciated. I can see where this issues might arise is serveral situations. John Hidey

tsuman_in · Answer

Admit it John you were really confused about every message. >;P

john · Answer

OK..thanks. I'm glad you replied with what you did. I was a bit confused on your first message. Thanks again.

chrishornberger · Answer

It's good practice in theory. What I'd do is expose a list of viable objects and the person using your code should supply an index into that array. I think you'll find it's more simple to work with and more usable. Don't get em wrong the dynamic enum's a nice idea but I don't think the complexity is worth the slight type-safe advantage you might get from it.

john · Answer

Thanks for everyones ideas and thought. Chornberger I'm not trying to isolate the other developers from good coding practice in fact I thought by exposing them an enumeration that I would be helping with good coding practice. I was always told to use an enumeration when possible to help avoid have to pass ints or data where errors can be made which the compiler can't catch. I do understand what your saying and think that even using a hashtable doesn't meet the requirements that I am shooting for. If it does please explain. What I need is to give a developer this class and when they call addUser and pass a parameter I would like that parameter to be bound to the database roles table. Not sure if good practice but I believe it is cause I am helping prevent any runtimes errors and not only prevent them but to catch them before compile time. Your thoughts??

chrishornberger · Answer

I think you're kinda going about it the wrong way. Alot of people seem to want to turn their backs on the back-end strengths of RDBMS systems. Provide a class that contains the Roles table entries and use that as a parameter to your adduser class if you want or simply use that to expose a readonly string[] or int[] of the roleids. But trying too hard to isolate other developers from good development practices will soon have your code being horribly over produced and hard to maintain. 1) throw some of the validation back on the db and 2) throw some of the ownness onto the developers you're writing this for.

john · Answer

But how could I sync this with the database after giving my class to another developer. For example the other developer would do a new myobject when they do this how would this know to sync with database at that time?

dip_2004_05 · Answer

John You can define a dynamic enum using reflection. The EnumBuilder class and EnumBuilder.DefineLiteral method can be used.. However I wouldn't use the logic as a preference... even though the framework gives you the flexibility to create run-time code structures you still want to be carefull in creating code structures at run time... it would be better to use a hashtable or similar collection sync'd with the db.. - dip

andrew · Answer

You can't do what you are trying to do. C# enumerations are statically typed and you can't extend them at runtime. So either you are stuck with predefined set of user roles or you can create a class called UserRoles that will hold the roles in hashtable. But then you lose static typing as you would have to provide a string or int to check for a role and you would have to do the validation yourself instead of compiler doing it for you.