LINQ basic query of relational data

As shown in the relational data, the LINQ statement is:

varquery= fromAinchdata. Awherea.admin== the incoming user name &&a.pwd==Incoming Password (you can pass in a model entity)Join Binchdata. B on a.bid equals b.id into AB fromR1inchAB. DefaultIfEmpty () Join Cinchdata. C on r1.cid equals c.id into BC fromR2inchBC. DefaultIfEmpty () Join Dinchdata. D on R2.did equals d.id into CD fromR3inchCD. DefaultIfEmpty ()

Select New            {//here is the ID of table A;Id =a.ID,//here is the name of table B;Name =R1. Name, Pro=R2. Pro, Ipadd=R3. Ipadd};//To the form of an array;        varList =query.tolist ();//List[0]. Name is the name of Table B for the first data that represents the result of the entire LINQ query, and so on;

Note : R1 can. All data out of Table B ... And so on

R2==table C;

R3==table D;

LINQ basic query of relational data