How the 01-entity framework controls data changes

All operational data in the Entity Framework is to update the entity state in the EF container

 Public enum entitystate    {        4,        8,        1,        0x10  ,        2    }

1. New

    New studentaddress            {                " address " + DateTime.Now            };            Db. Studentaddress.add (address);            Console.WriteLine (db. Entry<StudentAddress> (address). State); // added            Db. SaveChanges ();

Calling the Add method is essentially changing the entity state to added and then saving it to the database via SaveChanges ()

  New studentaddress            {                " address " + DateTime.Now            };            Db. Entry<StudentAddress> (address). state = System.Data.Entity.EntityState.Added;            Db. SaveChanges ();

2. Editing

--The first method:

            var address2 = db. Studentaddress.firstordefault ();             " ModifyFromEf2 "; //             db. SaveChanges ();

---1, compared to the value of the Entity field, does not produce a update-sql statement if the value is not changed
--2, modify a field value, update SQL statement will only set modify a field, do not modify all fields
--3, Query 2 times database

--The second method:

   New studentaddress            {                $,                "update address "            };             // 1, append to the EF container, the status is detached            var entityentry = db. Entry (address); //             entityentry.state = System.Data.Entity.EntityState.Modified;            Db. SaveChanges ();

--1, append a free entity to the EF container

--2. Change EF entity Status to Modified

--3. Modify all fields, regardless of change

--the third method (combined with the first two methods of modification):

--Query the database 1 times

--Modify the specified field

   //1, append to the EF container, the status is detached            varEntityentry = db. Entry (address);//DetachedConsole.WriteLine ("Append to EF container:"+entityentry.state); //2. Modify the specified field unchanged--> the specified field is modifiedDb. Studentaddress.attach (address);//equivalent to entry.   state = System.Data.EntityState.Unchanged; Console.WriteLine ("attach-unchanged:"+ entityentry.state);//unchangedEntityentry.property ("Address"). IsModified =true; Console.WriteLine ("post-modification status:"+ entityentry.state);//Modifieddb. SaveChanges ();

3. Deletion is also true

      New studentaddress            {                u222pdate,                "address " + DateTime.Now            };            Db. Studentaddress.attach (address); // Detached                   db. Studentaddress.remove (address); // or change its status to: entitystate.deleted;            Db. SaveChanges ();

4. Source code

--Each change in the data will have a corresponding set to hold the changes of these entities

such as: Objectstatemanager

Dictionary<entitykey, entityentry> _addedentitystore
Dictionary<entitykey, entityentry> _deletedentitystore
Dictionary<entitykey, entityentry> _unchangedentitystore
Dictionary<entitykey, entityentry> _modifiedentitystore

--When an entity change occurs, call Addentityentrytodictionary, insert into the collection

--Call SaveChange () to get these changes and manipulate the data

How the 01-entity framework controls data changes