Add, delete, modify, and query EF instances

Add, delete, modify, and query EF instances

Create a context object:WordBoradEntities db = new WordBoradEntities ();

Add:// 1.1Create object

User uObj = new User ()

{

UName ="Andy Lau",

ULoginName = "aaa ",

UPwd = "asdfasdfasdfsadf ",

UIsDel = false,

UAddtime = DateTime. Now

};

// 1.2PassEFAdd to database

// 1.2.1ObjectAddData ContextOfUserCollection

Db. Users. Add (uObj );

// 1.2.2Call data contextOfSaveObjectStored database

Db. SaveChanges ();

Query:List <User> list = db. Users. Where (u => u. uName ="Andy Lau"). ToList ();

Connection query:LinqConnection query:From a in db. User join B in db. UsersAddresses on a. Id equals B. udid

EFConnection query:IQueryable <UsersAddress> addrs = db. User. Include ("UsersAddresses"). Where (a => a. Id = 1 );

Another connection query:Var list = db. user. join (db. usersAddresses, c => c. id, g => g. udid, (c, g) => new {Name = c. name, GroupName = g. groupName });

Delete:EFThere are three ways to delete

Note: versions 1 and 2 are all deleted based on the primary key, and Version 3 is queried to the Database Based on any conditions and then deleted based on the query results, in fact, version 3 is deleted based on the primary key in the query results.

Version 1: Delete based on the primary key

//InstantiateUsersObject, and specifyIdValue

Users user = new Users () {Id = 1 };

//SetUserAttach to the context object and obtainEFContainer Management object

Var entry = db. Entry <User> (user );OrVar entry = db. Entry (user );

//Set the object status to delete

Entry. State = EntityState. Deleted;

//Save changes

Db. SaveChanges ();

Console. WriteLine ("Deleted successfully!");

Version 2: delete based on the primary key

//InstantiateUsersObject, and specifyIdValue

Users user = new Users () {Id = 1 };

//SetUserAttach to context object

Db. Users. Attach (user );

//DeleteUserObject

Db. Users. Remove (user );

//Save changes

Db. SaveChanges ();

Console. WriteLine ("Deleted successfully!");

Version 3: query the conditions and then delete them.

Var list = db. Users. Where (u => u. Name ="Zhang San");

If (list! = Null & list. Any ())

{

Foreach (User item in list)

{

Db. User. Remove (item );

}

}

Db. SaveChanges ();

 

Modify:

1.Officially recommendedModification Method (query first and then modify)

//SetIdIs2OfUsersData Extraction

Var user = db. Users. Where (u => u. Id = 2). FirstOrDefault ();

Console. WriteLine ("Before modification:"+ User. UserName );

//ModifyUserNameAttribute

User. UserName = "222222222222222 ";

//Save changes

Db. SaveChanges ();

Console. WriteLine ("After modification:"+ User. UserName );

2.Self-optimized modification method

// 1.Create an object to be modified

User use = new User () {uId = 8, uName ="Tom~~~ "};

// 2.SetObjectJoinEFContainer,And obtainCurrent objectOfStatus management object

DbEntityEntry <User> entry = db. Entry <User> (user );

// 3.SetThis objectModified

Entry. State = System. Data. EntityState. Unchanged;

// 4.SetThis objectOfUNameAttributeIsModify the status andEntry. StateChangedModifiedStatus

Entry. Property ("uName"). IsModified = true;

// 5.CloseEFObject validity check (if the created field of the data to be modified is not assigned a value, the object validity check is disabled. If all fields are assigned a value, the object validity check is disabled.EFObject validity check)

Db. Configuration. ValidateOnSaveEnabled = false;

// 6.Save to database again-- EfContextYesAccordingObjectStatus, AccordingEntry. State = ModifiedValueGenerateCorrespondingUpdate SQLStatement.

Db. SaveChanges ();

Console. WriteLine ("Modified successfully:");