LINQ to dataset (III)

ArticleDirectory

• Single Table query
• Connection Query
• LINQ to SQL

Single Table query

 
Datatable dt = Ds. tables ["product"]; var query = // call the asenumerable method to enable the LINQ able object to support LINQ query from R in DT. asenumerable () // use the field method in datarow. The field is generic and the ACCESS format is :. field <type> ("field name") Where R. field ("CID") = 2 select new {id = R. field ("ID"), name = R. field ("name"), cid = R. field ("CID")}; foreach (var p in query) {string MSG = string. format ("ID: {0}, name; {1}, CID: {2}", p. ID, P. name, P. CID); listbox1.items. add (MSG );}
 

Connection Query

Datatable dt_p = Ds. tables ["product"]; datatable dt_c = Ds. tables ["classify"]; var query = from C in dt_c.asenumerable () join P in dt_p.asenumerable () on C. field ("ID") equals P. field ("CID") Select New {id = P. field ("ID"), name = P. field ("name"), cid = P. field ("CID"), cname = C. field ("name")}; foreach (var p in query) {string MSG = string. format ("ID: {0}, name; {1}, CID: {2}, cname: {3}", p. ID, P. name, P. CID, P. cname); listbox1.items. add (MSG );}
 

Groupjoin

LINQ to SQL

First, create a LINQ to SQL class.

// LINQ to SQL class: including the classification table classify and product table productlq1datacontext LQ1 = new lq1datacontext (); // obtain all the classification var query = from C in lq1.classify select C; foreach (var c in query) {// note c. product is the product set foreach (var p in C. product) {// note p. classify. name is the product category name string MSG = string. format ("ID: {0}, name; {1}, category: {2},", p. ID, P. name, P. classify. name); listbox1.items. add (MSG );}}
 

Delete data

 
Lqdatacontext LQ1 = new lqdatacontext (); // method 1 // delete a product with the ID of 100 // delete_product is the Stored Procedure lq1.delete _ product (100) attached to lqdatacontext ); // method 2 // first find the record product PDT = (from P in product where p. id == 100 select P ). first (); // Delete this record lq1.product from the client cache. deleteonsubmit (PDT); // execute the command to delete lq1.submitchanges ();
 

Modify data

Lqdatacontext LQ1 = new lqdatacontext (); // Method 1: Stored Procedure // The parameters are product ID, name, price, quantity, and category idlq1.update _ product (100, "Nike", 99, 33, 2); // method 2 // first find this record product PDT = (from P in product where p. id == 100 select P ). first (); // modify this record PDT. name = "Nike"; PDT. price = 99; PDT. number = 33; PDT. cid = 2; // Delete lq1.submitchanges ();
 

Add data

 
Lqdatacontext LQ1 = new lqdatacontext (); // Method 1: Stored Procedure // method 2 Product PDT = new product (); PDT. id = 100pdt. name = "Nike"; PDT. price = 99; PDT. number = 33; PDT. cid = 2; lq1.product. insertonsubmit (p); lq1.submitchanges ();