modelBuilder.Entity<Department>().Property(p => p.RowVersion).IsRowVersion();

namespace ContosoUniversity.Models

{

    public class Department

    {
        [ConcurrencyCheck]

        public int DepartmentID { get; set; }

        [StringLength(, MinimumLength = )]

        public string Name { get; set; }

        [DataType(DataType.Currency)]

        [Column(TypeName = "money")]

        public decimal Budget { get; set; }

        [DataType(DataType.Date)]

        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]

        [Display(Name = "Start Date")]

        public DateTime StartDate { get; set; }

        public int? InstructorID { get; set; }

        [Timestamp]

        public byte[] RowVersion { get; set; }

        public virtual Instructor Administrator { get; set; }

        public virtual ICollection<Course> Courses { get; set; }

    }

}

   try
   {

          db.Entry(departmentToUpdate).OriginalValues["RowVersion"] = rowVersion;

          await db.SaveChangesAsync();

          return RedirectToAction("Index");

   }

   catch (DbUpdateConcurrencyException ex)

   {

          var entry = ex.Entries.Single();

          var clientValues = (Department)entry.Entity;

          var databaseEntry = entry.GetDatabaseValues();

          if (databaseEntry == null)

          {

              ModelState.AddModelError(string.Empty, "Unable to save changes. The department was deleted by another user.");

          }

          else

          {

              var databaseValues = (Department)databaseEntry.ToObject();

              if (databaseValues.Name != clientValues.Name)

              ModelState.AddModelError("Name", "Current value: "

               + databaseValues.Name);

               if (databaseValues.Budget != clientValues.Budget)

               ModelState.AddModelError("Budget", "Current value: "

               + String.Format("{0:c}", databaseValues.Budget));

               if (databaseValues.StartDate != clientValues.StartDate)

                ModelState.AddModelError("StartDate", "Current value: "

               + String.Format("{0:d}", databaseValues.StartDate));

               if (databaseValues.InstructorID != clientValues.InstructorID)

               ModelState.AddModelError("InstructorID", "Current value: "

                + db.Instructors.Find(databaseValues.InstructorID).FullName);

               ModelState.AddModelError(string.Empty, "The record you attempted to edit "

                            + "was modified by another user after you got the original value. The "

                            + "edit operation was canceled and the current values in the database "

                            + "have been displayed. If you still want to edit this record, click "

                            + "the Save button again. Otherwise click the Back to List hyperlink.");

               departmentToUpdate.RowVersion = databaseValues.RowVersion;

              }

    }

modelBuilder.Entity<Person>().Property(p => p.DepartmentID).IsConcurrencyToken();