EntityFramework 学习 一 Local Data

DBSet的Local属性提供简单的从context上下文获取当前已经被跟踪的实体（实体不能被标记为Deleted状态）

using System.Data.Entity;

class Program
    {
        static void  Main(string[] args)
        {

        using (var ctx = new SchoolDBEntities())
            {
                ctx.Students.Load();

                ctx.Students.Add(new Student() { StudentName = "New Student" });

                var std1 = ctx.Students.Find(); // find student whose id = 1
                ctx.Students.Remove(std1);// remove student whose id = 1

                var std2 = ctx.Students.Find(); // find student whose id = 1
                std2.StudentName = "Modified Name";

                // Loop over the students in context's local.
                Console.WriteLine("In Local: ");
                foreach (var student in ctx.Students.Local)
                {
                    Console.WriteLine("Found {0}: {1} with state {2}",
                                        student.StudentID, student.StudentName,
                                        ctx.Entry(student).State);
                }

                // Get all students from db.
                Console.WriteLine("\nIn DbSet query: ");
                foreach (var student in ctx.Students)
                {
                    Console.WriteLine("Found {0}: {1} with state {2}",
                                        student.StudentID, student.StudentName,
                                        ctx.Entry(student).State);
                }

            }
        }
    }

上面的例子中表明，本地数据保持跟踪状态为Added，Modified，Unchanged状态的实体

DBSet集合跟踪状态为Deleted，Modified，Unchanged实体