Question

I’m working on ASP.Net MVC3 web-site with Entity Framework and SQL Server 2008 as a data storage. Also I’m using Repository pattern to concentrate all data-access code in one area.

In my application I have many users, every user can have many Projects. User should only have access to their own projects.
At the moment I have this code:

    public IQueryable<Project> All
    {
        get { 
            return context.Projects
                .Where(p => p.Owner.ID == Util.GetCurrentUserID())
                .Select(p=>p); 
        }
    }

    public Project Find(System.Guid id)
    {
        return context.Projects
                .Where(p => p.Owner.ID == Util.GetCurrentUserID())
                .FirstOrDefault();
    }

If you noticed .Where(p => p.Owner.ID == Util.GetCurrentUserID()) is duplicated. And I have quite a few other places where these exact conditions are littered.

Is there a way in DbContext to have this condition always appended automatically to any query going Projects table?

Something like:

public class MyContext : DbContext
{
    public DbSet<Project> Projects
         .Where(p => p.Owner.ID == Util.GetCurrentUserID()) { get; set; }
}

OR

public class MyContext : DbContext
{
    public DbSet<Project> Projects { get {
           // Insert a cast from IQuerieable to DBSet below
       return Projects
              .Where(p => p.Owner.ID == Util.GetCurrentUserID())
              .Select(p => p);
    } 
    set; }
}

UPD while writing the question, realised that the last version can just work – need to try out. Still would like to hear other options for code optimisation and making it more DRY.

Thanks in advance!!

Answer 1

You can always write an extension method called “WhereProject”. Then call the standard “Where” method in your extension method after appending your condition to your predicate.

public static IEnumerable<TSource> WhereProject<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate) where TSource: Project
{
     return source.Where(p=> p.Owner.ID == Util.GetCurrentUserID() && predicate);
}

You can skip predicate if you want or set it as null in the parameter list for default value and then act accordingly if you don’t want to use predicate.

---

This is probably what you want, it is simple:

public static IEnumerable<TSource> WhereProject<TSource>(this IEnumerable<TSource> source) where TSource: Project
{
     return source.Where(p=> p.Owner.ID == Util.GetCurrentUserID());
}

EDIT
These solutions does not sound right to me. I think you would want to secure your row data one level higher, in my case it would be the service layer. Consider a method in your service class like this:

public List<Project> GetUserProjects(User user)
{
    return repo.All().Where(p => p.Owner.ID == Util.GetCurrentUserID()).ToList();
}

This way, from the method name, it is very clear what you are doing. It is not responsiblity of a repository to contain your specific logic. It is there to handle your data access only.