How do I centralize code shared by multiple Web API controllers? - asp.net

Question

I have close to 10 controllers that currently share the same code. The code is pretty simple, it just checks if a set of data is null and checks if the current user has permission to access the data.
If there is an issue, I throw an HttpResponseException.
The code works when it is sitting in each controller. I have also managed to centralize the code but I think the way I have done it is wrong. I've created a new class which inherits ApiController and then I have the controllers inheriting my new class. This is the only way I could get the HttpResponseExceptions working. Code is as follows:
//New centralized class:
public class AuthorizationClass : ApiController
{
private DataModel db = new DataModel();
public async Task checkUserisValid(int user_id)
{
user_list user_list = await db.user_list.FindAsync(user_id);
if (user_list == null)
{
throw new HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.BadRequest,"This user does not exist"));
}
int businessID = user_list.business_id;
var result = checkAccess(User.Identity.Name, businessID);
if (result.Count <= 0)
{
throw new HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.Unauthorized, "You do not have access to modify this business"));
}
}
public static List<user_details> checkAccess(string userName, int id)
{
//code which checks if the user is in the right tables
return checkAccess.ToList();
}
}
Then in the controller class, I have:
public class MyController : AuthorizationClass
{
public async Task<IHttpActionResult> Postnew_table(int id, new_table new_table)
{
await checkUserisValid(id);
//rest of controller
}
}
I tried to do it in different ways but this is the only way I could get it working with HttpResponseException. Is there a better way to do this without inheriting classes or is this the only way to do what I am after?
Thanks.

Answer 1

You could just move these 2 methods to some static helper class in a common assembly, you mention that Request is an instance variable on the controller, just pass it to the method.
public static class SomeHelper
{
public static async Task checkUserisValid(int user_id, DataModel db, Request request, User user)
{
user_list user_list = await db.user_list.FindAsync(user_id);
if (user_list == null)
{
throw new HttpResponseException(request.CreateErrorResponse(HttpStatusCode.BadRequest,"This user does not exist"));
}
int businessID = user_list.business_id;
var result = checkAccess(user.Identity.Name, businessID);
if (result.Count <= 0)
{
throw new HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.Unauthorized, "You do not have access to modify this business"));
}
}
public static List<user_details> checkAccess(string userName, int id)
{
//code which checks if the user is in the right tables
return checkAccess.ToList();
}
}