EF addition, deletion, query, and modification (iii) ------ release version, ef release version

EF addition, deletion, query, and modification (iii) ------ release version, ef release version

1. Add

1 # Add student information in region 1.1 (defined as Int type, and the number of affected rows is returned) 2 /// <summary> 3 // Add student information 4 /// </summary> 5 /// <param name = "stu"> </param> 6/ // <returns> </returns> 7 public int Add (Studnet stu) 8 {9 // Add the object to the EF context and obtain the status management object 10 DbEntityEntry <Studnet> entry = db. entry <Studnet> (stu); 11 12 // change the status to Added13 // introduce the System. data. entity14 entry. state = System. data. entityState. added; 15 16 // save to database 17 return db. saveChanges (); 18 19} 20 # endregion

2. Delete

2.1 Delete based on user ID

1 # region 2.0 Delete 2 // <summary> 3 // Delete 4 /// </summary> 5 // <param name = "id"> </param> 6 // <returns> </returns> 7 public int Delete (int id) 8 {9 Studnet stu = new Studnet () {s_ID = id}; 10 // Delete the passed ID11 // DbEntityEntry <Studnet> stu = db. studnets. where (s => s. s_ID = id) as DbEntityEntry <Studnet>; 12 DbEntityEntry <Studnet> entry = db. entry <Studnet> (stu); 13 // change the status to deleted14 entry. state = System. data. entityState. deleted; 15 16 // save to database 17 return db. saveChanges (); 18} 19 # endregion

2.2 Delete based on conditions

Actually, a lambda expression is passed in the where method, and the lambda expression is essentially an anonymous function.

1 # region 2.1 Delete 2 /// <summary> 3 // Delete 4 according to the conditions (any conditions are given and then deleted) 5 /// </summary> 6 /// <returns> </returns> 7 public int DeleteBy (System. linq. expressions. expression <Func <Studnet, bool> deleteWhere) 8 {
// Query the data to be deleted 9 List <Studnet> stuList = db. studnets. where (deleteWhere ). toList (); 10 // Delete 11 stuList cyclically. forEach (u => db. studnets. remove (u); 12 13 // save to database 14 return db. saveChanges (); 15 16} 17 # endregion

3. Modify

1 # modify region 3.0 2 /// <summary> 3 // modify 4 // notify the program of the attribute changed. Add a variable parameter array 5 /// </summary> 6 /// <param name = "stu"> </param> 7 /// <returns> </returns> 8 public int Modify (Studnet stu, params string [] parmeters) 9 {10 // Add the object to the EF container and obtain the status management object 11 DbEntityEntry <Studnet> entry = db. entry <Studnet> (stu); 12 13 // The object state is changed to Unchanged14 entry. state = System. data. entityState. unchanged; 15 foreach (string parms in parmeters) 16 {17 entry. property (parms ). isModified = true; 18} 19 20 return db. saveChanges (); 21} 22 # endregion

Test modification:

1 /// <summary> 2 // modified test 3 /// </summary> 4 public Student () 5 {6 // change the name of the student whose Id is 1 to xxxxxxxxxxx 7 Studnet stu = new Studnet () {s_ID = 1, s_Name = "xxxxxxxxxxx "}; 8 // modify the object and attribute 9 this. modify (stu, "s_Name"); 10}Test Modify

Test deletion:

1 // <summary> 2 // Delete Test 3 /// </summary> 4 public Student () 5 {6 7 this. deleteBy (u => u. s_ID = 1); 8}Test Delete

4. Query

4.1 query by condition

1 # region 4.1 query by condition 2 // <summary> 3 // query by condition 4 // the query results are generally set, therefore, the return value type is generic set 5 /// </summary> 6 /// <returns> </returns> 7 public List <Studnet> GetStudentList (System. linq. expressions. expression <Func <Studnet, bool> whereQuery) 8 {9 return db. studnets. where (whereQuery ). toList (); 10} 11 # endregion

4.2 grouping is required after the query is completed based on the condition.

1 // <summary> 2 // query by condition, group 3 more /// </summary> 4 /// <param name = "whereQuery"> </param> 5 /// <param name = "QroupByQuery"> </ param> 6 // <returns> </returns> 7 public List <Studnet> GetStudentList <Tkey> (System. linq. expressions. expression <Func <Studnet, bool> whereQuery, System. linq. expressions. expression <Func <Studnet, Tkey> QroupByQuery) 8 {9 return db. studnets. where (whereQuery ). orderBy (QroupByQuery ). toList (); 10}

 

Test query by condition:

1 public Student () 2 {3 this. GetStudentList (u => u. s_ID = 1 & u. s_Sex = ""); 4 5}Query by condition

Test query by condition. After query, group by condition:

1 public Student () 2 {3 4 this. GetStudentList (u => u. s_ID> = 1, u => u. s_Sex); 5}Query and group

4.3 paging Query

1 # region 4.2 query by page 2 // <summary> 3 // query by page 4 // sort first, page 5 /// </summary> 6 /// <param name = "pageIndex"> page number </param> 7 /// <param name = "pageSize"> capacity </param> 8 /// <param name = "orderLambda"> sorting condition </param> 9 /// <returns> </returns> 10 public List <Studnet> getPagedList <Tkey> (int pageIndex, int pageSize, Expression <Func <Studnet, Tkey> orderLambda) 11 {
// Pagination: You must note that OrderBy is required before Skip, because a RowNum paging query will be generated (which is listened through SQL ServerProfier) 12 return db. studnets. orderBy (orderLambda ). skip (pageIndex-1) * pageSize ). take (pageSize ). toList (); 13} 14 # endregion