public async Task<ActionResult> Edit(int? id, byte[] rowVersion)
        {
            string[] fieldsToBind = new string[] { "Name", "Budget", "StartDate", "InstructorID", "RowVersion" };

            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }

            var departmentToUpdate = await db.Departments.FindAsync(id);
            if (departmentToUpdate == null)
            {
                Department deletedDepartment = new Department();
                TryUpdateModel(deletedDepartment, fieldsToBind);
                ModelState.AddModelError(string.Empty,
                    "Unable to save changes. The department was deleted by another user.");
                ViewBag.InstructorID = new SelectList(db.Instructors, "ID", "FullName", deletedDepartment.InstructorID);
                return View(deletedDepartment);
            }

            if (TryUpdateModel(departmentToUpdate, fieldsToBind))
            {
                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;
                    }
                }
                catch (RetryLimitExceededException /* dex */)
                {
                    //Log the error (uncomment dex variable name and add a line here to write a log.
                    ModelState.AddModelError("", "Unable to save changes. Try again, and if the problem persists, see your system administrator.");
                }
            }
            ViewBag.InstructorID = new SelectList(db.Instructors, "ID", "FullName", departmentToUpdate.InstructorID);
            return View(departmentToUpdate);
        }
 public async Task<ActionResult> Delete(Department department)
 {
     try
     {
         db.Entry(department).State = EntityState.Deleted;
         await db.SaveChangesAsync();
         return RedirectToAction("Index");
     }
     catch (DbUpdateConcurrencyException)
     {
         return RedirectToAction("Delete", new { concurrencyError = true, id = department.DepartmentID });
     }
     catch (DataException /* dex */)
     {
         //Log the error (uncomment dex variable name after DataException and add a line here to write a log.
         ModelState.AddModelError(string.Empty, "Unable to delete. Try again, and if the problem persists contact your system administrator.");
         return View(department);
     }
 }