Entity framework: How to return a row from a table with composite keys?

问题

  public class UserBuilding
    {
        [Key, Column(Order = 0)]
        public int UserId { get; set; }
        [Key, Column(Order = 1)]
        public int BuildingId { get; set; }
        public int BuildingLevel { get; set; }
    }

If I wanted to return all the different buildings that belong to a user, I would do the following:

database.UserBuildings.Where(b => b.UserId == userId);

My question is what if I wanted to return a specific building from a specific user? What would be the most 'efficient' way of doing this? Is there a better way (such as a built-in function) than the following:

database.UserBuildings.Where(b => b.UserId == userId && b.BuildingId == buildingId);

回答1:

I think you are lookding for DbSet.Find method. This method finds entity by primary key. If you have composite primary key, then pass key values in the order they defined in model:

var userBuilding = database.UserBuildings.Find(userId, buildingId);

来源：https://stackoverflow.com/questions/14781777/entity-framework-how-to-return-a-row-from-a-table-with-composite-keys