UPDATE: With the addition of InExpression in EF6, the performance of processing Enumerable.Contains improved dramatically. The analysis in this answer is great but largely obsolete since 2013. Using Contains in Entity Framework is actually very slow. It’s true that it translates into an IN clause in SQL and that the SQL query itself is executed … Read more
No you cannot do that in mapping. Typical workaround is simple extension method: public static IQueryable<Car> BuildCar(this IQueryable<Car> query) { return query.Include(x => x.Wheels) .Include(x => x.Doors) .Include(x => x.Engine) .Include(x => x.Bumper) .Include(x => x.Windows); } Now every time you want to query Car with all relations you will just do: var query = … Read more
As already indicated by Ladislav in the comment, you need to disable automatic change detection to improve performance: context.Configuration.AutoDetectChangesEnabled = false; This change detection is enabled by default in the DbContext API. The reason why DbContext behaves so different from the ObjectContext API is that many more functions of the DbContext API will call DetectChanges … Read more
Right-click on the Solution from the Visual Studio Solution Explorer click the Manage Nuget packages for solution and install the EntityFramework
Try to use ColumnAttribute from System.ComponentModel.DataAnnotations (defined in EntityFramework.dll): [Column(TypeName=”Date”)] public DateTime ReportDate { get; set; }
Just call: something.OrderBy(r => Guid.NewGuid()).Take(5)
You can mark both ActivityID and ActivityName properties with Key annotation or you can use fluent API as described by @taylonr. Edit: This should work – composite key defined with annotations requires explicit column order: public class ActivityType { [Key, Column(Order = 0)] public int ActivityID { get; set; } [Key, Column(Order = 1)] [Required(ErrorMessage … Read more
If you have an Order class, adding a property that references another class in your model, for instance Customer should be enough to let EF know there’s a relationship in there: public class Order { public int ID { get; set; } // Some other properties // Foreign key to customer public virtual Customer Customer … Read more
You must make your foreign key nullable: public class User { public int Id { get; set; } public int? CountryId { get; set; } public virtual Country Country { get; set; } }
You are actually right. DbContext is an implementation of the unit of work pattern and IDbSet is an implementation of the repository pattern. Repositories are currently very popular and overused. Everybody use them just because there are dozens of articles about creating repository for entity framework but nobody actually describes challenges related to this decision. … Read more