entity framework query tutorial

[Original] Entity Framework query principle, entityframeworkPreface The full name of Entity Framework is ADO. NET Entity Framework, which is an ORM (Object/Relational Mapping)

Entity Framework Code First uses DbContext to query, entitydbcontext DbContext, DbSet, and DbQuery are three new classes introduced by Entity Framework Code First. DbContext is used to maintain database Session connections, track and save object changes, dbSet is used to tra

. Objectcontext.createqueryvar final = from E in entrieswhere e.name = = "Mark"Select E;var f = (system.data.objects.objectqueryvar s = f.totracestring ();return entries;}If you output the value of s, you can see:SELECT[Extent1]. [Simpleentryid] As[simpleentryid],[Extent1]. [Simpleentryname] As[simpleentryname]From[man]. [Myentry] AS[EXTENT1]WHERE N ' Mark ' = [Extent1]. [Simpleentryname]This is the typical TSQL generated by EF, and you will notice that the LINQ filter is applied to the SQL stat

'";Objectquery Entity Client From the diagram at the beginning of this article, it's easy to know whether you're using Entitysql or LINQ to Entities, and eventually entityclient to do the work. Of course, you can also use EntityClient directly,With Entitysql, performance is high, but manual tracking of data modification is done. So, only if 1. Requires high performance 2. When accessing data in read-only mode, consider using direct enti

the LINQ query in EF5. you can view the execution result of listing 13-20 to see its improved performance. In addition, as shown in listing 13-20, you can also disable the "automatic compilation" feature. You can use the underlying object objectcontext of the dbcontext object to get a reference to an object, set its enableplancaching attribute to false. To track each compiled query, EF traverses the

I recently re-learned Entity Framework. I saw a good learning tutorial. I will repost it here. The tutorial is as follows. Abstract: I recently studied Microsoft's ef. After studying this time, I feel that this EF is not perfect yet. It is a semi-finished product. However, it is said that in. net4.0, Microsoft will rec

Net 4 Entity Framework new query and Optimization Foreign key support (Foreign keys) Added external key support for Entity Framework. With foreign key Association, you can now include foreign key attributes in the entity, which si

" }; var methodquery = context. People.groupjoin (context. Persontypes,person => person. Persontypeid,persontype => Persontype.persontypeid, (person, type) = > new {person = Person,persontype = type}). SelectMany (groupeddata =>groupeddata.persontype.defaultifempty (), (group , persontype) = new {group. Person.lastname,group. Person.firstname,typename = persontype.typename?? " unknown " var query =from Oneperson in context. P

(CommandBehavior.SequentialAccess | CommandBehavior.CloseConnection)){while (RDR. Read ()){int a = RDR. GetInt32 (0);var B = rdr. GetString (1);Dict. Add (A, b);}}}Rsql + raw sql ... "pour directly into SQL into DB"People choose according to their hobbies ...3. Rsql:"1" repository in the Rsql query ....Curd operation ...1. R:var query = db. Students.sqlquery ("SELECT * from Student"). ToList ();"2" at data

First, let's briefly review how to use Code First. The first step is to first create an application on the console, and then add the Entity Framework through Nuget. The corresponding configuration will be added to packages. config and App. config at the same time. Step 2: Add a data operation context entity class. Add two constructors and add an object class of P

Foreign key support (Foreign keys) Added external key support for Entity Framework. With foreign key Association, you can now include foreign key attributes in the entity, which simplifies the development of key solutions such as data binding and N-tier development. You can directly use the foreign key property to set the relationship between objects: Code hig

Original: About MySQL Entity Framework 6 execute like query problem solutionI am not good at words, straight to the pointEnvironment: Ef6.0.0.0+mysql server5.6+mysqlconnector6.9.5.0The problem points are as follows:1 varUsername ="Admin";2 varLST = Userservice.getquery (). Where (p =p.username.contains (UserName));3 foreach(varUserinchls

Entity FrameWork addition, deletion, query, modification, entityframework Add 1 # Add + void Add () 2 in region 1.0 /// 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 tool

the Cartesian product. In a one-to-many scenario, the data for the main table is duplicated.Right connection as long as the apple and the banana in the order of the swap is OH.Let's wrap it up. The SQL statement generated by EF is flexible, and the content of select is very much affected by the last generated inner join or left join. The above is for reference only, of course, left connection, right connection and other wording. Fully connected The whole connection how to write, a

The Entity framework is a good thing, although not as powerful as hibernate, but easier to use. Today, we'll take a look at how common SQL is expressed in EF, and the Func form and LINQ form are listed (I prefer the Func form).1, simple query:Sql:SELECT * from [clients] WHERE Type=1 and Deleted=0ORDER by IDEf://func FormvarClients = CTX. Clients.where (c = C.type = =1 c.deleted = =0) . (c=c.id).

Label:First, Introduction EF supports the open bottom of the ADO framework, DbContext has three common methods Dbset.sqlquery//Queries and returns entities dbcontext.database.sqlquery Second, usage 1. Dbset.sqlquery usage var list = db.admins.SqlQuery ("SELECT * from admin"); foreach (var item in list) { Response.Write (item.username); Response.Write ("); } 2. Dbcontext.

'. ' Lasteditip ', ' Extent1 '. ' Password ', ' Extent1 '. ' Realname ', ' Extent1 '. ' Statusid ', ' Extent1 '. ' TypeId ', ' Extent1 '. ' UserName ' from 'UserasWHERE (LOCATE (TRIM ( ' Admin ' > 0 Although not translated into like query, but translated into a locate query!! It's a wonderful, expert explanation.But locate query efficiency is higher tha

Entity FrameWork addition, deletion, query, modification, entityframework Add 1 # Add + void Add () 2 in region 1.0 /// 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 tool

Current Paging Support single table PublicIlist out intTotal, expressionBOOL>> filter =NULL, funcNULL,intindex =1,intSize = -)whereTEntity:class { intSkipcount = (Index-1) *size; var_reset =Get (filter, by); Total=_reset. Count (); _reset= Skipcount >0?_reset. Skip (Skipcount). Take (size): _reset. Take (size); return_reset. ToList (); } PublicIqueryableBOOL>> filter =NULL, funcNULL)whereTEntity:class{IQueryable(); if(Filter! =NULL) {

using (var ObjectContext = new Agentsystementities ()) { DateTime dt = new DateTime (1997, 1, 1); string entitysql = "Select VALUE users from users WHERE users.adddatetime > @dt;"; Objectparameter[] PS = { new ObjectParameter ("DT", DT)}; objectquery String message = "executed statement:" + query.commandtext + "\n\r"; if (query. Count () > 0) { Message + = query. First ().UserNames +