Code-First Development with Entity Framework 4 (July 16th) .. by ronaldweinland.info team here. In this post, I assume you already setup your machine. Initial Entity Framework Code First Migration Step by Step . ronaldweinland.info that gives developers an automated mechanism for accessing & storing the data in the. MANIPULATING DATA USING THE ENTITY FRAMEWORK concepts using a technology such as ronaldweinland.info Although every attempt is made to ex- able when working with the Entity Framework: model first, database first, and code first .
|Language:||English, Spanish, Japanese|
|Genre:||Business & Career|
|ePub File Size:||22.79 MB|
|PDF File Size:||20.48 MB|
|Distribution:||Free* [*Register to download]|
ronaldweinland.info Entity Framework provides a strongly-typed LINQ data access experience over relational databases, including direct, efficient access. ronaldweinland.info Entity Framework is from Microsoft. Entity Framework vs LINQ-to-SQL modeling techniques using Entity Framework like code first, model first or. the ronaldweinland.info Entity Framework. Understanding relative positioning. R&D Team .. Provides a Code First experience to create entity models using code.
NET Entity Framework is a framework for providing object-relational mapping service on data models. Entity Framework addresses the impedance mismatch between the relational database format and the client's preferred object format. Language Integrated Query LINQ defines a set of operators that can be used to query, project, and filter data in arrays, enumerable classes, XML, relational databases, and other data sources. NET developer. It abstracts the database's data model from the application's data model. Working with object-relational data becomes easier with Entity Framework's tools.
When using keys, you can set this to determine if you want this key to be an identity or a computed value. Type Set to String by default.
Sets the datatype of the property and supports almost all SQL Server datatypes. Unicode Set to True by default, giving you the Unicode versions of the datatypes. Determines whether you will get an nvarchar or a varchar. Creating Associations Once you flesh out your entities, you need a way to associate them.
In SQL Server, you would simply add foreign keys to the tables. In EF, you need to create associations. The Add Association dialog box opens. In the Add Association dialog box, you can set the two endpoints for both sides of the association as well as the association type. In this example, a one-to-many association between Person and Address is being set up.
Using the Multiplicity drop-down menus, select different association types. Checking the Navigation Property checkboxes allows you to set navigation properties to be used when navigating the associations. By default, these are set to pluralized or not based on the type of association. You can rename these to more descriptive names if you want. In this example, checking this box would add a PersonId to the address table.
It is important to note that the key that gets added will be a concatenation of the primary key entity name and the primary key itself.
If the key was left as simply Id, the foreign key field would be PersonId. Section 4 Inserting Entities Now that you have a model, you can start putting some data in it.
To create a new person, you must create a new person object. Once you have created the new object, simply add it to the context and then call SaveChanges on the context. In this example, there is address data to add to the person object before saving. Add address ; context. AddObject person ; context. When SaveChanges is called, the context will inspect any objects it is tracking and decide what steps to take and what order to do them in.
In this example, there are two entities that are new and they have to be submitted in the proper order. Since Address is dependent on Person because of a foreign key constraint, the person must be added first. The EF ensures that they are added in the proper order. The SaveChanges call is automatically wrapped in a transaction.
As such, if anything fails on insert, the whole thing will roll back and an exception will be thrown. To generate your database, right click on the design surface and select Generate Database From Model.
A dialog box opens where you can select the database location just as you did when adding from an existing database. Click Next to view a preview of the SQL file that will be generated.
Click Finish to generate the file. It is important to note that the generated SQL file contains create statements only and does not look at the current state of your database to determine what updates need to be done.
It is recommended that you run this file against a compare database and then use a SQL compare tool to sync the schemas. Section 5 Querying Entities Once you have data in the database, you can get the data back out. You will need to have some familiarity with LINQ and the various available options to take advantage of what the EF has to offer.
There are resources online and in print to help you should you need it. Below is a basic LINQ query that will give you all of the person data. People; The second option is much cleaner; and unless you need to do joins or any other special LINQ operations, the second method is recommended.
Be aware that lazy loading will create more database connections than you may expect. For example, if there were two people in the database, the above code would call the database three times—once for the initial call and once for each person when the Addresses collection gets checked.
You can turn lazy loading off in the properties window for global options. You can also turn off lazy loading on a call-by-call basis by setting the ContextOptions.
LazyLoadingEnabled property to false. If performance is not an issue, you can leave lazy loading enabled since it will make development quicker by not having to request the additional data. If you need to control the database hits, you have a couple of options.
If you plan on serializing the classes, you will want to turn lazy loading off. To get at association data without using lazy loading, you can use eager loading and explicit loading. With eager loading, you can load the data up front in one trip to the database.
With explicit loading, you can load associated data on demand.
This will use more bandwidth upfront, but it will be limited to one round trip. Load ; foreach var address in person. You can use a mix of all three methods depending on the requirements of the application. In Entity Framework, parameter binding by name is supported. Binding by position is not supported. Entity data models can now be generated from Oracle database schemas. Oracle supports Database First and Model First modeling approaches. Specifying filters on the Visual Studio Server Explorer data connection enables the Entity Data Model Wizard to also filter Oracle database objects that are fetched and displayed.
These Oracle function imports can return a collection of scalar, complex, and entity types, including returning an Oracle implicit result set as an entity type.
It also includes the facets for each EDM type. NET does not support Time literals and canonical functions related to the Time type. Developers were firmly entrenched in one camp or the other and felt free to viciously and usually anonymously flame the non-believers in forums, comments and blog posts.
Now, it seems, every software development tool will soon just work with every other software development tool. We're heading for one big, happy family of developers. Anyway, back to the news of special importance to you data developers. The Release 4 "introduces tools and data provider support for ADO. The release's database client works with Oracle Database 9.