Entity freamwork Learning

 

 

Http://www.cnblogs.com/qouoww/archive/2012/01/05/2313231.html (excellent introduction blog)

Http://weblogs.asp.net/manavi/archive/2011/01/03/inheritance-mapping-strategies-with-entity-framework-code-first-ctp5-part-3-table-per-concrete-type-tpc-and-choosing-strategy-guidelines.aspx

Http://www.cnblogs.com/wlflovenet/archive/2011/08/08.html

Http://www.cnblogs.com/LingzhiSun/

 

Http://code.msdn.microsoft.com/EFProviderWrappers-c0b88f32 about processing with Level 2 Cache and logging SQL logs

Http://www.codeproject.com/Articles/435142/Entity-Framework-Second-Level-Caching-with-DbConte Level 2 Cache and records SQL logsCodeExample

Http://www.cnblogs.com/LingzhiSun/archive/2011/05/24/EFPowerTool_1.html entityfreamwork gadgets, this person's blog is pretty good

 

Http://www.dotblogs.com.tw/code6421/archive/2010/09/02/17526.aspx update the specified field does not need to be queried first

Http://www.cnblogs.com/dudu/archive/2011/04/06/2006709.html update the specified field does not need to be queried first

 

_ The above is more effective. _ The following is average.

Link http://blog.sina.com.cn/s/blog_8a5695250100ti25.html

1. directly execute SQL statements

In general, EF does not need to write SQL statements, but in some cases, for example, it is not satisfied with the generated SQL statements to be optimized or it is necessary to write abnormal SQL statements during report statistics.

In this case, the vulnerabilities of Using ORM are revealed in batch operations. However, as an excellent ORM framework, EF provides three methods to support the original SQL.

1.Dbset. sqlquery query with tracking status

2.Dbdatabase. sqlquery queries with no trace status

3.Dbdatabase. sqlcommand directly executes SQL statements, which are generally used for batch addition, deletion, and modification.

Next let's take a look at the usage

Add a method to the public resource library in the previous article

PublicVirtualIenumerable<Tentity>Getwithrawsql (StringQuery,ParamsObject  [] Parameters ){Return Dbset. sqlquery (query, parameters );}PublicVirtualIenumerable<Tentity>Getwhithdbsql (StringQuery,ParamsObject  [] Parameters ){ReturnContext. database. sqlquery<Tentity> (Query, parameters );}  

The difference between the first and the second is described through comparison ~~

Execute these two methods in the course controller.

 VaR Query="Select * from course where courseid = @ P0"  ; Course course=  Unitofwork. courserepository. getwithrawsql (query, ID). Single (); entitystate state= Unitofwork. getstate (course );StringName=  Course. Department. Name; course coursetwo=  Unitofwork. courserepository. getwhithdbsql (query, ID). Single (); entitystate statetwo=  Unitofwork. getstate (coursetwo );StringNametwo=Coursetwo. Department. Name;  

Result After execution

1. First, check that the first State is unchanged. That is to say, he adds the context and has a trace state.

And the following can be read smoothlyCourse. Department. Name, that is, the navigation attribute can be read.

2. Check that the second State is that detached is not addedNo trace status in context Context

Therefore, the following error will be reported when reading the content of the navigation attribute ~~

3. Let's talk about it again.Dbdatabase. sqlcommand: This is relatively simple to add, delete, and use. This is good. Here is an example of batch update ~

If you need to update all course credits to N, it will be inconvenient to use the ORM framework in this batch operation. In this case, we can use this to directly execute SQL statements.

This business belongs to the course, so it inherits the general resource library Class Code as follows:

 Using  System;Using Contosouniversity. models;Namespace  Contosouniversity. Dal {PublicClassCourserepository: genericrepository<Course>  {  Public  Courserepository (schoolcontext context ):Base (Context ){}PublicIntUpdatecoursecredits (Int  Multiplier ){ReturnContext. database. executesqlcommand ("Update course set credits = credits * {0}"  , Multiplier );}}}  

Modify the previousUnitofwork class

 Private Courserepository;Public  Courserepository {Get  {  If(This. Courserepository=Null ){This. Courserepository=New  Courserepository (context );}Return  }}  

The Controller is as follows:

PublicActionresult updatecoursecredits (Int?Multiplier ){If(Multiplier! =Null) {Viewbag. rowsaffected=Unitofwork. courserepository. updatecoursecredits (multiplier. Value );}ReturnView ();} 
 

Add a view ~~

Running result Diagram

Ii. No trace Query

What is tracing query enabled for EF by default? Let's take a look at the following code.

 Department duplicatedepartment=  DB. Orders ments. Where (d=>D. instructorid=  Department. instructorid). firstordefault (); duplicatedepartment. Name="Wuhawuha"  ;  bool   isupdate  =  dB. entry     Department  >  (duplicatedepartment ). property (P  =>   P. name ). ismodified; // whether to modify   string   now  =  dB. entry     Department  >  (duplicatedepartment ). property (P  => P. Name). currentvalue; // Current ValueStringBefore=DB. Entry<Department>(Duplicatedepartment). Property (P=>P. Name). originalvalue; // previous value  

We first randomly find out a department information and modify his name. This is what we will use the above information to get the current value. The previous value. This is what we do. Let's see what we didn't do.

It is easy to add a trace-free configuration during query.Asnotracking ()You can. After adding the parameter, we can see that it has changed but isupdate is still false. In addition, an exception is thrown when the previous value is obtained.

In general, we do not need to track these statuses. we can remove the trace query during the query to improve the performance ~ I used to think that removing this will affect the use of navigation attributes, but it will not be affected after testing ~

This tracing query also brings about another problem. See the figure below.

This is because an error is reported if you add a statement before the modification to query the modification and then modify it.An object with the same key already exists in objectstatemanager. Objectstatemanager cannot trace multiple objects with the same key.

When this error occurs, addAsnotracking ()You can. At present, I do not like tracing when using EF ~~ Like to addAsnotracking ()

3. Use proxy

After understanding the orm framework, we know that the navigation attribute uses the proxy mode, which is also related to the navigation attribute. Disabling proxy can speed up serialization.

The code for disabling proxy adds the following code to the class that inherits dbcontext

PublicSchoolcontext ()
{This. Configuration. proxycreationenabled=False;} 
 

The following shows the differences between agent and agent.

Our administrator is a navigation attribute. We can see a long string of numbers and letters. When we access this administrator attribute below, we will get the Administrator attribute through delayed loading.

Let's look at the figure when the proxy is disabled.

If all of our navigation attributes are null, the navigation attributes cannot be obtained correctly.

Iv. Automatic Detection

• Dbset. Find
• Dbset. Local
• Dbset. Remove
• Dbset. Add
• Dbset. Attach
• Dbcontext. savechanges
• Dbcontext. getvalidationerrors
• Dbcontext. Entry
• Dbchangetracker. Entries

In the preceding method, the automatic detection function is called. This feature is enabled by default. we can disable this feature during batch operations to improve performance. For example:

 Using(VAR Context=New  Unicornscontext ()){Try {Context. configuration. autodetectchangesenabled  =False  ;//Make calls callin a loop  Foreach(VAR unicornIn  Myunicorns) {context. Unicorns. Add (UNICORN );}}Finally {Context. configuration. autodetectchangesenabled  =True  ;}}  

 

Http://kb.cnblogs.com/page/98712/

Http://blogs.msdn.com/ B /adonet/archive/2011/03/15/ef-4-1-code-first-walkthrough.aspx official

Http://blogs.msdn.com/ B /adonet/archive/2011/02/04/using-dbcontext-in-ef-feature-ctp5-part-10-raw-sql-queries.aspx

Http://www.cnblogs.com/haogj/archive/2011/05/09/2040196.html

 

Http://kb.cnblogs.com/page/127199/ EF FAQ

Reprinted from: http://www.cnblogs.com/shanyou/archive/2011/07/17/2108953.html

 

To support the design-centric development process, EF4 also supports code-centric development, code-first Development supports a more elegant development process, which allows you:

• Develop without using the designer or defining an XML ing file.
• You can write a simple model object poco (plain old classes) without the need for a base class.
• The database persistence layer does not require any configuration through "conventions are better than configurations"
• You can also overwrite "conventions are better than configurations" and use Smooth APIs to completely customize the persistence layer ing.

After using the code first mode, you can say that you no longer need the data model automatically generated by the. edmx system in your project.

ChineseArticle:

EF framework step by step (3)-code-firstef framework step by step (7)-code first dataannotations (1) EF framework step by step (8) -Code first dataannotations (2) EF framework step by step (9)-code first fluent API

Entity Framework 4.1 code first (1)

Entity Framework 4.1 code first (2)

Entity Framework 4.1 code first (3)

Entity Framework 4.1 code first (4)

Entity Framework 4.1 code first (5)

Endless. Net 4.0 (9)-code first of ADO. NET Entity Framework 4.1

EF code-first custom table ing

Entity Framework code first user's gospel-one of EF power tool's usage notes

Efmvc-ASP. net mvc 3 and Entity Framework 4.1 code first Project Introduction

Use EF code first and ASP. NET mvc3 for class-level model verification

Control entityframework4.1 code-first by yourself to gradually eliminate the strange phenomenon of EF

You can control entityframework4.1 code-first by yourself. It has multiple powerful loading methods for EF.

Indecisive about Entity Framework

Collection of Entity Framework Problems

Summary of Entity Framework queries

In-depth analysis of Entity Framework

Mvc3 + ef4.1 Learning Series

English article:

The repository pattern with EF code first & dependeny injection in ASP. NET mvc3

Entity Framework Code-first, odata & Windows Phone Client

An open source ASP. net mvc 3 blog engine

Http://weblog.codeplex.com/