How to choose a class whose method to call

Question

Hi all, I would appreciate a hand in designing my code. So far I haven't found a way to do this. I have a number of classes for different entities (currently 7 but there can be more in the future). I need a method in each of these classes that authorizes user's access to a file resource. Implementation varies but an exception must be thrown if user does not have access to the file in question. Problem is, when a file is being accessed, I need to call the authorization method of the correct class based on the data on the file. Files are stored in a db table and one of the fields in that table determines which entity the file is related to and how to find which user has access to the file. So I must read the file data from db, then see which entity it's related to and then call the authorization method of the correct class. Is there a way in C# to accomplish this without having to make a switch case structure on the file field value? Example of the classes used: public class FileAttachment { // other FileAttachment class stuff protected void AuthorizeFileAccess(FileAttachmentData file) { // file has a field which tells which entity it relates to // here I need to choose which class to use based on the file data } } // simplified example of a related entity public class ChatMessage { public int SenderUserId; public int RecipientUserId; // here I need a method that checks that chat message sender's or recipient's // user id matches the user id of the logged in user // if not, throw exception } And this is what I want to avoid: switch (file.SourceValue) { case "ChatMessageAttachmentFile" : var cm = new ChatMessage(); cm.AuthorizeAttachmentAccess(); case "OtherAttachmentFile" : var other = new SomeOtherClass(); other.AuthorizeAttachmentAccess(); default : throw new Exception( "Access denied" ); }

Pirjo Ahvenainen · Answer

Hi, Thanks for your reply. What you suggest is actually something we have in place, user is authenticated using the .Net Identity framework and has claims but I must implement file authorization this way due to reasons in the software architecture that cause restrictions on what I can do. The code I'm using would locate inside the OnActionExecuting method of a custom AuthorizeAttribute or in this case a bit deeper into the code structure to make sure the authorization is done regardless of files being accessed via the mvc website controller actions or a an API, or even some other way. The main problem is to make a structure where each authorization method are in their own classes and I need to call the authorization method of the correct class based on the file source value. I thought maybe I could utilize System.Action in some way but I'm not quite sure if that's the optimal solution.

Ronika Jency · Answer

Hi, you can implement Identity server mechanism . token - comibnation of user claim(detils) + secret key each user must have the access token to acess the cs file. using Authorize keyword you can access the web api cs file.