Basic usage methods for the. NET Entity Framework

Build model

There are two ways to query EF, a LINQ query, a lambda expression

            // Common Query Linq mode             from  in Db. Set<book>()                       where53                       select  b;             // Normal query Lambda mode            Iqueryable<book> List1 = db. Set<book>()                53);

            //Multi-table query Linq            varList = fromBookinchDb. Set<book>() Join BookTypeinchDb. Set<booktype>() on book. TypeId equals Booktype.typeidSelect New{book}; //Multi-table query lambda            varList = db. Set<book>()                . Where (U= U.bookid >2&& U.typeid = =4)                . Join (db. Set<BookType> (), book = Book. TYPEID, TP = TP. TypeId, (book, TP) =New{book, TP});

            //Query database only when deferred load is used .iqueryable<book> list = db. Set<book>()                . OrderByDescending (U= U.bookid)//The expression method in the IQueryable object converts the lambda expression to an expression object by default. Skip (2)                . Take (3); //no delay loading because IEnumerable has no way to stitch up full SQL statementsIenumerable<book> List1 = db. Set<book>()                . AsEnumerable ()//Turn the result into a IEnumerable type. OrderByDescending (U =u.bookid). Skip (2)                . Take (3);

Add data

[HttpPost] PublicActionResult Add (book book) {DbContext db=NewDbmodel (); Db. Set<Book>().            ADD (book); //returns the number of rows affected            if(Db. SaveChanges () >0)            {                returnJson (New{msg="Add Success"                }); }Else            {                returnJson (New{msg="Add failed"                }); }        }

modifying data

        [HttpPost]        public  actionresult Edit (book BB) {            new  Dbmodel ();             // Attach the object to the context  state set to not change the            db. Set<book>(). Attach (BB);             = entitystate.modified;            Db. SaveChanges ();             return Json (new            {                " modified successfully "            });        

Delete data

         Public ActionResult Delete (int  ID) {            new  Dbmodel ();             = db. Set<book> (). FirstOrDefault (b = B.bookid = = ID);            Db. Set<Book>(). Remove (book);            Db. SaveChanges ();             return Json (new            {                " Delete succeeded "            }, jsonrequestbehavior.allowget);        }

Basic usage methods for the. NET Entity Framework