Entity Framework additions and deletions and transactional operations

1. Add Objects

            Dbentity db = new dbentity ();            Create an object entity, note that all properties need to be assigned (in addition to the auto-grow primary key), if not assigned, the database will be set to null (note whether it is nullable)            var user = new user                {                    Name = "Bomo", Age                    = +,                    Gender = "Male"                };            Db. User.add (user);            Db. SaveChanges ();

2. Delete the object, delete the primary key that only needs the object

            Dbentity db = new dbentity ();            Delete only need primary key, here Delete the primary key is 5 of the row            var user = new User {Id = 5};            Attaches an entity to the object Manager in            db. User.attach (user);            Method one:            db. User.remove (user);            Method Two: Change the state of the current entity to delete            //db. Entry (user). state = entitystate.deleted;            Db. SaveChanges ();

3. Modify the Object

Method One:

            Dbentity db = new dbentity ();            The modification needs to assign a value to the primary key, note: All fields need to be assigned, the field without assignment is updated with NULL to the database            var user = new user                {                    Id = 5,                    Name = "Bomo", age                    = 21 ,                    Gender = "male"                };            Attaches an entity to the object Manager in            db. User.attach (user);            Change the state of the current entity to modified            db. Entry (user). state = entitystate.modified;            Db. SaveChanges ();

Method Two: Every time the method one needs to modify all the fields, inefficient, and troublesome, the following describes the modification of some fields

            Dbentity db = new dbentity ();            The modification needs to assign a value to the primary key, note: All fields need to be assigned, the field without assignment is updated with NULL to the database            var user = new user                {                    Id = 5,                    Name = "Bomo", age                    = 21                };            Attaches an entity to the object Manager in            db. User.attach (user);                        Gets the state entity to user and can modify its state            var setentry = ((iobjectcontextadapter) db). ObjectContext.ObjectStateManager.GetObjectStateEntry (user);            Only the Name property of the entity and The Age attribute            setentry.setmodifiedproperty ("name") are modified;            Setentry.setmodifiedproperty ("Age");            Db. SaveChanges ();

4. Use transactions: It is very simple to use transactions, just put the required operations in TransactionScope, and finally commit

            Dbentity db = new dbentity ();            using (var scope = new TransactionScope ())            {                //Perform multiple operations                var user1 = new User                {                    Name = "Bomo", age                    =                    Gender = "male"                };                Db. User.add (user1);                Db. SaveChanges ();                                var user2 = new User                {                    Name = "Toroto", age                    = $,                    Gender = "female"                };                Db. User.add (user2);                Db. SaveChanges ();                Commit TRANSACTION                scope.complete ();            }

5, Query: Query through LINQ query

            Dbentity db = new dbentity ();            Select the partial field            var user = db. User.where (U = u.name = = "Bomo"). Select (U + = new {Id = u.id, Name = u.name, age = U.age}). FirstOrDefault ();            Only functions that call FirstOrDefault, first, single, ToList, ToArray, and so on will execute queries against the database.

Entity Framework additions and deletions and transactional operations