LinQ to SQL

ORM (O-object object, r-relation relationship, m-mapping mapping)

Table name-Class name

Column name--property name

Table relationships-member objects of a class

linq--Integrated Query Language sql--Structured Query language

LINQ includes: LINQ to SQL, LINQ to Object, LINQ to DataSet, LINQ to Entity

LinQ to SQL

Step one: Build a LINQ to SQL Class (project right → add → class → data, LINQ to SQL class → add a database connection in Server Explorer → find the table you want, drag to the page)

Step Two: Instantiate the context object.

Step Three: Operation

1. Increase:

            //Instantiation ContextMydbdatacontext context =NewMydbdatacontext (); //1. Making ObjectsInfo data =NewInfo (); Data. Code="p211"; Data. Name="Zhou Qing"; Data. Nation="N001"; Data. Sex=false; Data. Birthday=NewDateTime (1990,1,1); //2. Register the newly created object in the contextcontext.Info.InsertOnSubmit (data); //3. Submit the data to the databaseContext. SubmitChanges ();

2. By deleting:

Mydbdatacontext context =NewMydbdatacontext (); //1, in the Info Table query Code "p003" Data            varQ = context.Info.Where (p = = P.code = ="p003");//var q is a dynamic deduction type that automatically infers the data type. (p = = P.code = = "p003") meaning: The data in P is passed in (p. Code = = "P003") to Judge            if(Q.count () >0) {Info data=Q.first (); //2. Registrationcontext. Work.deleteallonsubmit (data.                work); Context. Family.deleteallonsubmit (data.                Family);                Context.Info.DeleteOnSubmit (data); //3. Submit to Databasecontext.            SubmitChanges (); }

3. Change:

        Static voidMain (string[] args) {Mydbdatacontext Context=NewMydbdatacontext (); //1, in the Info table to find the code "P001" data, put in memory            varQ = context.Info.Where (p = = P.code = ="P001"); if(Q.count () >0) {Info data=Q.first (); //2. Modify the data in memoryData. Name ="Mr. Hu"; Data. Nation="n001"; Data. Sex=false; //3. Submit the modified data to the databasecontext.            SubmitChanges (); }        }

4, check: 4.1, check all

        Static voidMain (string[] args) {Mydbdatacontext Context=NewMydbdatacontext (); //1. Query all data in info table            varQ =context.            Info; //2. Display            foreach(Info datainchq) {//data. Nation1: The national object that the current person corresponds to. Console.WriteLine (data. name+"\ t"+data.                Nation1.name); //data. Work: A collection of working records for the current person                foreach(Work workinchdata. Work) {Console.WriteLine ("\ t"+work. firm+"\ t"+Work .                Depart); }            }        }

4.2. Search by condition

            var " p211 ");    // the default is to return the collection            if 0)    // See if the data is found in the collection             {                = Q.first ();    // take the first object out                of the Console.WriteLine (data. Nation1.name + data. Name);            }

Mydbdatacontext context =NewMydbdatacontext (); //Query All            varQ = fromPinchContext. InfoSelectp; varQ =context.            Info; //single-condition query            varQ = fromPinchContext. InfowhereP.code = ="p003" Selectp; varQ = context.Info.Where (p = = P.code = ="p003"); //Multi-Criteria Query            varQ = fromPinchContext. CarwhereP.price > -&& P.brand = ="b002" Selectp; varQ = Context. Car.where (p = p.price > -&& P.brand = ="b002");//effect is the same as the next line            varQ = Context. Car.where (p = p.price > -). Where (p = = P.brand = ="b002");//lambda expression (the most streamlined function)            varQ = fromPinchContext. CarwhereP.price > -|| P.brand = ="b002" Selectp; varQ = Context. Car.where (p = p.price > -|| P.brand = ="b002"); //Fuzzy Query            varQ = fromPinchContext. CarwhereP.name.contains ("5")SelectP//include            varQ = fromPinchContext. CarwhereP.name.startswith ("Audi")SelectP//Start            varQ = fromPinchContext. CarwhereP.name.endswith ("Audi")SelectP//End            varQ = Context. Car.where (p = p.name.contains ("5"));//include            varQ = Context. Car.where (p = p.name.startswith ("Audi"));//Start            varQ = Context. Car.where (p = p.name.endswith ("type"));//End            varQ = fromPinchContext. CarwhereP.name.substring (2,1) =="5" SelectP//a third character            varQ = Context. Car.where (p = p.name.substring (2,1) =="5");//The third character is a 5//DISTINCT Query            varQ = ( fromPinchContext. CarSelectP.brand). Distinct ();//Go heavy            varQ = Context. Car.select (p = p.brand). Distinct ();//Go heavy//Connection Query--the association between objects is the point.             varQ = Context. Car.where (p = p.brand1.productor.prod_name = ="FAW Toyota"); //page Out            varQuery = context. Car.skip (2*4). Take (4); //Sort            varQuery = context. Car.orderby (p = p.price);//Ascending            varQuery = context. Car.orderbydescending (p = p.price);//Descending//Collection Operations            varQuery1 = context. Car.where (p = p.brand1.productor.prod_name = ="FAW Toyota"); varQuery2 = context. Car.where (p = p.price > -); //intersection            varquery =Query1.            Intersect (Query2); //and set            varquery =Query1.            Union (Query2); //Difference Set            varquery =Query1.            Except (Query2); //complement set            varQuery = context. Car.except (Query1);

            // Linq2sql            New Mydbdatacontext ();            List<Car> list = context. Car.tolist ();    // turn into a            collection // linq2object--to In-memory collection operations            var query = list. (p = p.price);    // Sort by Price

LinQ to SQL