[Reprint] C # LINQ to SQL

1,Concat (connecting different sets does not automatically filter the same item. Will delay calculation)

var q = (from c in db.Customers        select c.Phone            ).Concat(            from e in db.Employees            select e.HomePhone);   var q = (from c in db.Customers            select new            {               Name = c.CustomerName,               Phone = c.Phone             }).Concat(            from e in db.Employees            select new            {               Name = e.EmployeeName,               Phone = e.HomePhone             });

 

2,Union (merge to automatically filter identical items. Will delay calculation)

var q = (from c in db.Customers            select c.Country).Union(            from e in db.Employees            select e.Country);

 

3,Intersect (intersection. Will delay calculation)

var q = (from c in db.Customers            select c.Country).Intersect(            from e in db.Employees            select e.Country);

4,T (difference, a-B. Exclude A from B from a set. Will delay calculation)

var q = (from c in db.Customers            select c.Country).Except(            from e in db.Employees            select e.Country);

 

5,Top and bottom (fetch a specified amount of data. Will delay calculation)

 

6,Take (obtain the first n data of the set. Will delay calculation)

var q = (from e in db.Employees            orderby e.HireDate            selct e).Take(5);

 

7,Skip (skip the first n data records of the set. Will delay calculation)

var q = (from p in db.Products            orderby p.UnitPrice descending            select p).Skip(10);

Select All products other than the 10 most expensive products

 

8,Takewhile (it is not obtained until a condition is invalid. Will delay calculation)
That is, use its conditions to determine the elements in the source sequence in sequence, and return the elements that meet the judgment conditions. The judgment operation ends at the end of the returned false or source sequence.

 

9,Skipwhile (same as above)

 

10,Paging)

var q = (from c in db.Customers             orderby c.CustomerName             select c).Skip(50).Take(10);

 

11,Like

var q = from c in db.Customers　　　　    where SqlMethods.Like(c.CustomerID, "C%")　　　　    select c;

Query Consumers whose consumer IDs do not have the "axoxt" format:

var q = from c in db.Customers　　　　    where !SqlMethods.Like(c.CustomerID, "A_O_T")　　　　    select c;DateDiffDay

Compare two time variables. There are: datediffday, datediffhour, datediffmillisecond, datediffminute, datediffmonth, datediffsecond, datediffyear:

var q = from o in db.Orders　　    　　where SqlMethod.DateDiffDay(o.OrderDate, o.ShippedDate) < 10　　　　    select o;

Query all orders delivered within 10 days after the order is created

 

12,Compiled query (pre-compiled query)

NorthwindDataContext db = new NorthwindDataContext();    var fn = CompiledQuery.Compile(               (NorthwindDataContext db2, string city) =>　　            from c in db2.Customers　　            where c.City == city　　            select c);    var londonCusts = fn(db, "London");    var seaCusts = fn(db, "Seattle");