默认情况下,ef在datacontext生命周期中跟踪已加载的实体
当操作数据库现有数据时,才会跟踪
如果在datacontext回收之前没savechanges,那么跟踪的状态就会丢失.
实体得要有主键属性才能跟踪
可以用下面的方法来跟踪datacontext的状态(Added Modified Deleted Unchanged Detached)
private static void DisplayTrackedEntities(DbChangeTracker changeTracker) { var entries = changeTracker.Entries(); foreach (var entry in entries) { Console.WriteLine("Entity Name: {0}", entry.Entity.GetType().FullName); Console.WriteLine("Status: {0}", entry.State); } }
输出Added
using (var context = new BookStore()) { Console.WriteLine("Adding Author"); Author author = new Author() { Name = "Mark" }; context.Authors.Add(author); Console.WriteLine("Context tracking changes of {0} entities.", context.ChangeTracker.Entries().Count()); DisplayTrackedEntities(context.ChangeTracker); }
输出Modified
using (var context = new BookStore()) { Console.WriteLine("Update Author"); Author author = context.Authors .FirstOrDefault(); author.Name = "Russell"; Console.WriteLine("Context tracking changes of {0} entities.", context.ChangeTracker.Entries().Count()); DisplayTrackedEntities(context.ChangeTracker); }
输出Deleted
using (var context = new BookStore()) { Console.WriteLine("Delete Author"); Author author = context.Authors .FirstOrDefault(); context.Authors.Remove(author); Console.WriteLine("Context tracking changes of {0} entities.", context.ChangeTracker.Entries().Count()); DisplayTrackedEntities(context.ChangeTracker); }
输出Unchanged
using (var context = new BookStore()) { Author author = context.Authors .FirstOrDefault(); Console.WriteLine("Context tracking changes of {0} entities.", context.ChangeTracker.Entries().Count()); DisplayTrackedEntities(context.ChangeTracker); }
输出Detached
Author author; using(var context = new BookStore()) { author = context.Authors .FirstOrDefault(); } using (var context = new BookStore()) { Console.Write(context.Entry(author).State); }
原文：https://www.cnblogs.com/nocanstillbb/p/11494560.html