Non-static method requires a target. Entity Framework 5 Code First

The problem boiled down to the query. My original question had this query:

var allPartners = DbContext.User
                       .Include(u => u.Businesses)
                       .Where(u => u.Businesses.Any(x => x.Id == currentBusinessId))
                       .ToList();

Which wasn’t quite accurate, I had in fact removed the error in an attempt to ask my question succinctly. The query was actually:

var currentBusiness = GetBusiness();
var allPartners = DbContext.User
                       .Include(u => u.Businesses)
                       .Where(u => u.Businesses.Any(x => x.Id == currentBusiness.Id))
                       .ToList();

When the GetBusiness method returned null the error was thrown. Simply ensuring that I don’t pass a null object into the expression made the error stop.