Entity FrameWork addition, deletion, query, modification, entityframework

Entity FrameWork addition, deletion, query, modification, entityframework

Add

 

1 # Add + void Add () 2 in region 1.0 /// <summary> 3 // Add 4 /// </summary> 5 static void Add () 6 {7 // 1. create an object and use the object initialization tool to initialize the object 8 Studnet stu = new Studnet () 9 {10 // assign the field name 11 s_Name = "Liu Dehua ", 12 s_Sex = "male", 13 s_Age = c_ID = 16}; 17 18 // 2. create an EF data context object and add it to the database through EF. 19 DB_USERSEntities db = new DB_USERSEntities (); 20 21 22/3 Add the object stu to 23 db in the Student set of the data context. studnet. add (stu); 24 25 // 4. call the data context storage method to save the object to the database 26 db. saveChanges (); 27 28 // ------ test code -------------- 29 Console. writeLine ("added successfully"); 30 31} 32 # endregionAdd

Modify

 

The modification is intelligent. When you generate an SQL statement, you only generate an SQL statement for the field of a modified column. You can use the SQL Server profiler tool in the SQLServer toolbar to listen to it.

1 # modify region 2.0 (query before modification) 2 // <summary> 3 // modify -- (for modification, according to the official standard, the data to be modified is first queried and then modified.) 4 // </summary> 5 static void Modify () 6 {7 // create the data context object 8 DB_USERSEntities db = new DB_USERSEntities (); 9 10 // FirstOrDefault the first element of the returned result 11 Studnet stu = db. studnet. where (s => s. s_ID = 10 ). firstOrDefault (); 12 13 Console. writeLine (string. format ("the information before modification is {0}:", stu. toString (); 14 15 // modify data 16 stu. s_Name = "Zhang huimei"; 17 18 // save it to database 19 db. saveChanges (); 20 21 // ------ test code ---------------------------------- // 22 Console. writeLine ("modified successfully"); 23 Console. writeLine (string. format ("the modified information is {0}:", stu. toString (); 24} 25 26 # endregionModify

Query

 

// The query result is an object, which is similar to system. What. This is because the ToString () method is the Object method. here we need to rewrite a Tostring method for the Student Object.
// Because the T4 template will automatically overwrite the previous changes and regenerate each time it is saved. Therefore, you need to write a partial category for student and rewrite the Tostring () method in the partial category.

1 # region 3.0 simple Query 2 // <summary> 3 // Query 4 /// </summary> 5 static void Query () 6 {7 // create the data context object 8 DB_USERSEntities db = new DB_USERSEntities (); 9 10 // query 11 List <Studnet> stu = db. studnet. where (s => s. s_Name = "Andy Lau "). toList (); 12 13 // ------ test code ------------------------------------------ // 14 // traverse the queried data 15 stu. forEach (s => Console. writeLine (s. toString (); 16} 17 # endregionQuery

Delete

 

 

// Deletion is also the same as modification. You need to first find the data to be deleted and then delete it, but this is not the case here.

1 # region 4.0 Delete 2 /// <summary> 3 // Delete 4 /// </summary> 5 static void Delete () 6 {7 DB_USERSEntities db = new DB_USERSEntities (); 8 9 // test the deletion of specified data (create the object to be deleted) 10 Studnet stu = new Studnet () {s_ID = 8}; 11 // attach to 12 db in EF. studnet. attach (stu); 13 // mark as deleting 14 db. studnet. remove (stu); 15 // Delete 16 db. saveChanges (); 17 18 // -------- test code --------------- // 19 Console. writeLine ("deleted successfully"); 20 21} 22 # endregionDelete