ef增刪改查的四種方式

先自定義一個查詢語句

int[] nums = new int[7] { 1, 2, 3, 4, 5, 6, 7 };
            //var onum = from int n in nums where n % 2 == 0 select n;
            //foreach (var item in onum)
            //{
            //    Console.WriteLine(item);
            //}
            //Console.Read();
            //查詢用戶的角色以及名稱含有主任的

下面是幾鍾常見查詢方法

            RbacDBEntities db = new RbacDBEntities();
            //var user = from UserInfo p in db.UserInfos where p.Name.Contains("主任") select p;

            //using (db)
            //{
            //    var n = db.UserInfos.Where(p => p.Name.Contains("主任")).Select(p => new { p.Name,roleName=p.Role.Name}).ToList();
            //    foreach (var item in n)
            //    {
            //        Console.WriteLine(item.Name+"\t"+item.roleName);
            //    }
            //    Console.Read();
            //}
            //顯示各角色的用戶數 顯示角色id 用戶數量
            //var num = from  n in db.UserInfos
            //          group n by n.RoleID into g
            //          select new { roleID=g.Key, nums = g.Count() };
            //        foreach (var item in num)
            //        {
            //            Console.WriteLine(item.roleID +"\t"+item.nums);
            //        }

            //用戶數
            //var man = db.UserInfos.Count();

            //    Console.WriteLine(man);

幾個基本函數

            ////roleID最小值
            //var min = db.UserInfos.Min(p => p.RoleID);
            //Console.WriteLine("最小值："+min);
            //var max = db.UserInfos.Max(p => p.RoleID);
            //Console.WriteLine("最大值：" + max);
            //var sum = db.UserInfos.Sum(p => p.RoleID);
            //Console.WriteLine("和：" + sum);
            //var avg = db.UserInfos.Average(p => p.RoleID);
            //Console.WriteLine("平均值：" + avg);
            //Console.Read();

新增，修改，刪除的方法

            //string sql = @"insert into roles values('院長','局級幹部')";
            //int res = db.Database.ExecuteSqlCommand(sql);
            //if (res > 0)
            //{
            //    Console.WriteLine("新增成功");

            //}
            //string sql = @"update roles set Remark=@remark where id=@id6 ";
            //SqlParameter[] pare = {
            //    new SqlParameter("@remark","廳級幹部"),
            //    new SqlParameter("@id6","6")

            //};
            //int result = db.Database.ExecuteSqlCommand(sql, pare);
            //if (result > 0)
            //{
            //    Console.WriteLine("更新成功");
            //}
            //string sql = "delete from roles where id=7";
            //int result = db.Database.ExecuteSqlCommand(sql);
            //if (result > 0)
            //{
            //    Console.WriteLine("刪除成功");
            //}
            //獲取數據insertRoles
            db.insertRoles("方法4", "備註4");

            //Role role = new Role()
            //{
            //    Name = "方法1",
            //    Remark = "備註1"

            //};
            //db.Entry(role).State = System.Data.Entity.EntityState.Unchanged;
            //db.SaveChanges();

            //var role = db.Roles.Find(1);
            //role.Name = "方法1";
            //role.Remark = "備註2";
            //db.SaveChanges();

            //string sql = @"update roles set Remark=@remark where id=@id6 ";
            //SqlParameter[] pare = {
            //    new SqlParameter("@remark","方法3"),
            //    new SqlParameter("@id6","6")

            //};
            //int result = db.Database.ExecuteSqlCommand(sql, pare);
            //if (result > 0)
            //{
            //    Console.WriteLine("更新成功");
            //}

            //db.updateRoles(1,"方法4", "備註4");

            //刪除方法1
            //var role = db.Roles.Find(1);
            //db.Entry(role).State = System.Data.Entity.EntityState.Deleted;
            //db.SaveChanges();

            //刪除方法2
            //var role = db.Roles.Find(1);
            //db.Roles.Remove(role);
            //db.SaveChanges();

            //刪除方法3
            db.deleteRoles(1, "方法3", "備註3");
            Console.Read();
            ```