Entity Framework 5 - only select entities where entity IsActive

Question

Using the Code First approach I have created a number of different entities that inherit from an interface IConcurrent with a property IsActive for example:

public class Currency : IConcurrent
{
    public string CurrencyId { get; set; }

    public string Description { get; set; }

    public bool IsActive { get; set; }
}

Each time I select entities I find myself always having to include a conditional clause such as this real basic example:

db.Currencies.Where(c => c.IsActive);

My question is that is it possible to some how intercept/hook into the DbContext so that my LINQ queries will always return IsActive == true for entities that inherit the IConcurrent interface, to avoid having to explicitly add .Where(c => c.IsActive) each time?

So far I've looked at the possible methods to override in DbContext which none of them seem to fit the bill. Can anyone help?

Answer 1

You can use filtering on the Set<> method to get just active instances, something along the lines of:

public IQueryable<T> GetActive<T>() where T : class, IConcurrent
{
   return Set<T>().Where(e => e.IsActive);
}

This method could be included in a class that inherits the DbContext class, or you could make it into an extension method, like:

public static DbContextExtensions
{
  public static IQueryable<T> GetActive<T>(this DbContext context) 
    where T : class, IConcurrent
  {
     return context.Set<T>().Where(e => e.IsActive);
  }
}

Answer 2

Conditional mapping is supported in Model First approach but it is not directly supported in Code first approach. You may have a workaround by creating a property in DBContext similar to the following;

public IQueryable<Currency> ActiveCurrencies 
{
    get 
    {
        db.Currencies.Where(c => c.IsActive);
    }
}