LINQ to SQL additions and deletions

ORM "Object Relation Mapping"

Linq to SQL:

First, build the LINQ to SQL class:
Understanding Context Classes: Linq to SQL class name +context each table in the database can be accessed using a context class;

Classification Application *******************************************************
Note: 1 info is the actual referenced table name
2 You need to instantiate the context class first when performing a function.

★★★★★★★★★★★★★★★★★★★★, query class ★★★★★★★★★★★★★★★★★★★★★★★★★
Mydbdatacontext context= New Mydbcontext (),//instantiate the context class
1 queries All and displays
Mydbdatacontext context= new Mydbcontext ();//Instantiate the context class
List<info> list = Context.info.tolist (); Perform a query operation;
Datagridview1.datasouse = list;//display the queried data
2 single condition query--equivalent query
var mama = from P in context. Info wher E P.code = = "n002" SELECT p//query mode one
var mama = context.info where (p=>p.code== "n002");//query mode two lambda expression

Datagridview1.datasouce = Mama//Send to page display;
3 single-condition query----not equivalent query
var mama = from P in Context.info where p.code! = "N0 "Select P//Fayi
var mama = context.info where (P=>p.code!=n002);//Fah lambda expression
var mama = context.info WH ere (p = = datatime.now-p.birthday.values.year); Method of extracting time

Datagridview1.datasouce = Mama//Send to page display;
over 4 pieces of query:
//var query = from P in _context.info where p.sex = = true & amp;& p.birthday.value.year > 1985 Select P; French one
//var query = _context.info.where (p=>p.sex==true && p.birthday.value.year>1985); method two LANBDA expression
var query = _context.info.where (p = = P.sex = True). Where (p=>p.birthday.value.year>1985); Multi-conditional logic with a chained expression can be used to write
Datagridview1.datasource = query;
5 fuzzy query:
var mama = from P in Context.info where P.name Co Ntains ("Zhang") selsect p;//equivalent to like '% of% ' fuzzy query--information containing what characters
//var query = from P in _context.info where P.name.startswith ( "Zhang") select P; Like ' sheet% ' fuzzy query--information beginning with what character

//var query = from P in _context.info where P.name.endswith ("Zhang") select P;//like ' % ' Fuzzy query--what character ends with information
//var query = from P in _context.info where p.name.substring (total) = = "Zhang" select p;//like ' _ Sheet% ' mode Paste Query--The information of what character is a number

var query = _context.info.where (p = = P.name.startswith ("Zhang"));
6 Set operation:
var q1 = from P in _context.info where p.sex== true select P;
var q2 = _context.info.where (P = p. Birthday.Value.Year > 1985);

Intersection: var query = Q1. Intersect (Q2);
Set: var query = Q1. Union (Q2);
Difference set: var query = Q2. Except (Q1);
7 Statistical functions:

var query = _context.info.where (p = = p.birthday.value.year > 1985);
//this. Text = query. Count (). ToString (); Number of
//this. Text = query. Sum (p=>datetime.now.year-p.birthday.value.year). ToString (); Sum
//this. Text = query. Average (p = datetime.now.year-p.birthday.value.year). ToString ();//averaging
//this. Text = query. Max (p = datetime.now.year-p.birthday.value.year). ToString (); The maximum value of
this. Text = query. Min (p = datetime.now.year-p.birthday.value.year). ToString (); To find the minimum value

7 Conversion actions:
var mama = from P in Context.info where P.name contains "Zhang" select p;

list<info> list = Mama. ToList (); To convert the query results to a generic collection:
info[] List = Mama. ToArray (); Convert the results of the query into arrays;
Info data = Mama.tosingle (); Convert query results to a single object
Info data= mama.tofirst (); Convert query results to a single object

8 Paging the query results
How many pagesize per page, to find the first few pages PageNo
var query = _context.info.skip (2*3). Take (2); From the query results skip (jump) 2 rows per row 3 records to take the jump 2 rows;

Datagridview1.datasource = query;
9 Special Usage Records
1 Removing duplicate statements from a query: var mama = from P in Convert.info where P.name contains "Zhang" select p. distinct ();

★★★★★★★★★★★★★★★★★★★★ Add Class ★★★★★★★★★★★★★★★★★★★★★★★★★
Add action:
Mydbdatacontext context= New Mydbconte XT ();//Instantiate the context class
Info data = new info ();//The table you want to add is instantiated first;
data. Code = Txtcode.text; To initialize
data. Name = txtName.Text;
Data.sex =convert.toboolean (textsex.text);
Data.nation =txtnation.text;
Data. Birthday = Convert.todatetime (Textbirthday.text);

Context.info.insertOnSubmit (data);//Tell the context class to perform an insert operation when clicking Submit;

Context.submitchanges ();//context submission to database

★★★★★★★★★★★★★★★★★★★★ Delete class ★★★★★★★★★★★★★★★★★★★★★★★★★
Delete
//Find the object to be deleted by the context class
Mydbdatacontext C ontext= new Mydbcontext ();//Instantiate the context class
var sc = from mama in Context.info where Mama. Code Select Mama;
if (Sc.count () >0)
Info data = Sc.first ();
//Tell context
Context.info.delectOnsubmit (data);
//Context class Commit To the Database
Context.submitchangs ();

★★★★★★★★★★★★★★★★★★★★ Four, modify the class ★★★★★★★★★★★★★★★★★★★★★★★★★
Modify Operation
Mydbdatacontext context= new Mydbcontext ();//Instantiate the context class
Find the data you want to modify
var Tianjia = from mama in context.info where p.code = = Txtcode.text Select Mama
modifying data
Data. Name = txtName.Text;
Data. Sex = Convert.toboolean (Txtsex.text);
Data. Nation = Txtnation.text;
Data. Birthday = Convert.todatetime (Txtbirthday.text);
Context class commits to the database
Context.submitchanges ();

LINQ to SQL additions and deletions