多租户实体过滤

Question

I'm working on multi-tenant application where different companies are differs by CompanyID column. There are also common core tables in database like Settings which are the same for all the companies. I have two base persistent classes: PersistentObject and CompanyPersistentObject . The last one inherits from the first and adds CompanyId property. I'm going to insert company ID criteria directly in repository like this:

public class EntityFrameworkRepository<T> : Repository<T>
    where T : PersistentObject
{
    private readonly DbSet<T> set;
    private readonly IApplicationContext applicationContext;
    private readonly IQueryable<T> queryable;

    public EntityFrameworkRepository(DbSet<T> set,
                                     IApplicationContext applicationContext)
    {
        this.set = set;
        this.applicationContext = applicationContext;

        if (typeof (CompanyPersistentObject).IsAssignableFrom(typeof(T)))
        {
            // TODO: Apply CompanyPersistentObject filter
            // using applicationContext.CompanyID
        }
    }
}

Is this good approach or you can suggest the better solution?
If so how to inject the criteria for CompanyPersistentObject in DbSet<T> where T is PersistentObject and have no CompanyId property?

Answer 1

I do almost exactly what you are proposing in my application. The method I found trickiest to implement was the "All" wrapper. I wanted to return an IQueryable but linq to entities does not support casting to entities. The answer to that problem was provided here:

How to conditionally filter IQueryable by type using generic repository pattern

I did actually start out using the technique that Martin Eden suggests, but I re-factored it into a single base repository as you are proposing, and it is now much simpler and safer.

This is what my "Find" method looks like:

    public virtual T Find(int id)
    {
        T e = Context.Set<T>().Find(id);

        var od = e as OrganisationDependent;
        if (od != null && od.OrganisationID != CurrentOrganisationID)
            return null;

        if (e == null)
            return null;

        return e;
    }

Answer 2

I would suggest that you instead extend your EntityFrameworkRepository class with a CompanyRepository class that has this behaviour. Then you could constrain the type parameter of CompanyRepository to only be classes that extend CompanyPersistentObject (or better, an interface).

For example:

public class EntityFrameworkRepository<T> : Repository<T>
    where T : PersistentObject
{
    private readonly DbSet<T> set;
    private readonly IApplicationContext applicationContext;
    private readonly IQueryable<T> queryable;

    public EntityFrameworkRepository(DbSet<T> set,
                                 IApplicationContext applicationContext)
    {
        this.set = set;
        this.applicationContext = applicationContext;
    }
}


public class CompanyRepository<T> : Repository<T>
    where T : PersistentObject, ICompany
{
    public CompanyRepository(DbSet<T> set,
                                 IApplicationContext applicationContext)
    {
        this.set = setFilteredById(set, applicationContext.CompanyId);    
    }
}