entity framework query tutorial

This section briefly introducesObjectcontext, Objectquery,Objectstateentry,ObjectstatemanagerThese important classes are all located under the system. data. Data. entity. dll namespace system. Data. Objects. In subsequent chapters, we often use some of their methods to accomplish some of our operations or purposes. In this section, we will briefly describe the methods of various classes that we may use in the future to facilitate our subsequent study.

which new additions can be performed correctly, as follows:Model1container context = new Model1container (); var Objsetone = context. Entityones; Objsetone.addobject (New Entityone () {ID = 2, P1 = "Pp1", P2 = "Pp2", P3 = "PP3", Entitytwo = new Entitytwo () {id=2, T1 = "Tt1", T2 = "Tt2", T3 = "tt3"}); Context. SaveChanges ();Note that you can only succeed if you complete the new Entityone and associated attribute entitytwo at the same time, but is this the reali

much as possible, there is a very simple principle, that is, try to use the LINQ and lambda expressions so that EF can help us translate. There are two types of count in C. Enumerable. Count () is a method, and list. Count is an attribute. Once a thing becomes a list, you can count it again, and it must be in the memory. Therefore, in EF, to perform the Count operation, write as follows: context.Post.Count(p => p.Categories.Any(q => q.Name == categoryName)); In this case, count () accepts a Lam

URLs. For details about how to use it, refer to the help documentation on Yang Tao's homepage. The following code shows how to get Entity Framework to return the paging query result. IQueryable It is also very simple, that is, the Skip () method and the Take () method are used to obtain the data after pagination.

In 《Entityframework-Based Domain-driven design practices [continued]: Use Cases of domain-driven design practices based on EF 4.3.1 code firstIn the article, I gave a field-driven design practice case based on Entity Framework 4.3.1 code first: byteart retail. This case has attracted the attention of many readers and many netizens have asked questions about various implementation technologies in the case. I

map method, we first select the attributes of the class, and then map the selected Attribute list to a database table. We add a new unit test in our test program to test whether Entity Framework code first persists this class instance to two tables. [TestMethod] public void CanAddNewProductCatalogWithPhoto() { OrderSystemContext unitOfWork = new OrderSystemContext();

Expanded the functional class library of the Entity Framework.https://github.com/loresoft/EntityFramework.Extended1 Batch Update/delete1) Delete// Delete all users where FirstName matches " FirstName ");2) Update//Update All Tasks with the status of 1 to status of 2context. Tasks.update (t= = T.statusid = =1, T2=NewTask {Statusid =2});//example of using a IQueryable as the filter for the updatevarUsers = context. Users.where (U = u.firstname = ="First

Essence of Entity FrameWork delayed loading (1), entityframework 1. The standard query operator method of the set is an extension method added to the IEnumerable interface in System. Linq. Enumerable. 2. The standard query operator method in DBSet 3. one of the essential reasons for delayed loading: currently, multipl

method just created: Using System; using System. collections. generic; using System. linq; using System. text; using ProductEFDemo. business; namespace ProductEFDemo. presenter {public static class UpdateDateView {public static void UpdateProductUnitByUnitName () {try {Console. writeLine ("prepare to update data... "); UpdateData. updateProductUnitByUnitName (); Console. writeLine ("Update successful! ");} Catch (System. exception ex) {Console. writeLine (String. format ("error, error message:

= Info.id, Title = Info.title, Description = Info.description, postdatetime = Info.posttime}; Listview_alternative. DataSource = Infolist.topagedquery (pageSize, pagenumber); listview_alternative. DataBind (); }}protected void aspnetpager1_pagechanged (object sender, EventArgs e) {binddata (aspnetpager1.pagesize, Aspnetpager1.currentpageindex)} It's easy to use! First you need to tell Aspnetpager how many records are in the data you want to bind, and then get the paging data through

LINQ Technology (LINQ to Entities) enables developers to create flexible, strongly typed queries directly from the development environment for Entity Framework object contexts by using LINQ Expressions and LINQ standard query operators. LINQ to Entities queries use the object service infrastructure. The ObjectContext class is the main class that interacts with th

. This will produce a large number of statements, and the efficiency will certainly be low. The solution is to execute SQL statements directly, and write an extension method on your own. although many people disagree with this method. but I personally prefer to write an extension method myself. in this way, there are two benefits. first, it is easy for developers to use. second, convenient management. some netizens have suggested using ObjectStateManager. changeObjectState is used for batch dele

uses LINQ to SQL to query the table for user information in the username containing the input string. The 8th, 9, and 10 lines are the way LINQ is queried.1 Public voidDisplayuserbyname ()2 {3 stringUserName =string. Empty;4Console.WriteLine ("Input UserName:");5UserName =console.readline ();6Userdal Userdal =NewUserdal ();7ListuserDal.users.ToList ();8 varquery = fromBinchUsers9 whereb.u

Entity Framework Dynamic ConditionsProblem: In the actual coding process, depending on the selection situation, you will need to query the data set according to different conditionssuch as: State Confirmstatus, if empty, query all, if there is a specific value, query the cor

Linqpad lets you query Entity Framework models that you define in Visual Studio. In a nutshell, here's how to proceed: CreateADO. NET Entity Data ModelIn a Visual Studio project, and build. From linqpad, clickAdd connection(Top left) SetData ContextDropdownCustom Enti