Fluent API - Relationships - EF6 | Microsoft Docs
First, Lazy loading isn't always faster. Specially if you are "A" entity" has 1: n relation to "B" entity but "B" entity has n: m relation to "C" entity. And if I wouldnt. First, let's simply review the feature rollout of EF over time. . Entity Framework is still locked, step by step, to the way the underlying data store works. Therefore we must account for those behaviors in our code breaking the. Here, we will learn how to configure One-to-Many relationships between two entities (domain classes) in Entity Framework 6.x using the code-first approach.
In the absence of such a rule, you can usually combine both tables into one table without breaking any normalization rules. To understand one-to-one relationships, we create two entities, one is User and another is UserProfile.
One user can have a single profile, a User table that will have a primary key and that same key will be both primary and foreign keys for the UserProfile table. Core project under the Data folder.
Our User class code snippet is as in the following: Now, we define the configuration for both entities that will be used when the database table will be created by the entity. The configuration defines another class library project EF.
Data under the Mapping folder. Now create two configuration classes for each entity. For the User entity, we create the UserMap entity. This is done using the modelbuilder in an override of the OnModelCreate method. So let's see each method used in the constructor one-by-one. The Haskey method configures a primary key on table.
The Property method configures attributes for each property belonging to an entity or complex type. It is used to obtain a configuration object for a given property. The options on the configuration object are specific to the type being configured. It configures how values for the property are generated by the database.Entity Framework Relationships Code First
DatabaseGeneratedOption is the database annotation. It enumerates a database generated option. Identity is used to create an auto-increment column in the table by a unique value.
Configures the table name that this entity type is mapped to. Configures a required relationship from this entity type. Instances of the entity type will not be able to be saved to the database unless this relationship is specified.
Fluent API - Relationships
The foreign key in the database will be non-nullable. The entity type being configured will be the dependent and contain a foreign key to the principal. The entity type that the relationship targets will be the principal in the relationship.
Now define the connection string in App. Data project so that we can create database with the appropriate name. In this class, we override the OnModelCreating method. This method is called when the model for a context class EFDbContext has been initialized, but before the model has been locked down and used to initialize the context such that the model can be further configured before it is locked down.
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The following is the code snippet for the context class. The conventions are defined in the System. You can further configure your model by using data annotations or the fluent API. Precedence is given to configuration through the fluent API followed by data annotations and then conventions. This topic provides an overview of the conventions used by Code First. Type Discovery When using Code First development you usually begin by writing.
NET Framework classes that define your conceptual domain model. In addition to defining the classes, you also need to let DbContext know which types you want to include in the model. To do this, you define a context class that derives from DbContext and exposes DbSet properties for the types that you want to be part of the model. Code First will include these types and also will pull in any referenced types, even if the referenced types are defined in a different assembly.
If your types participate in an inheritance hierarchy, it is enough to define a DbSet property for the base class, and the derived types will be automatically included, if they are in the same assembly as the base class. In the following example, there is only one DbSet property defined on the SchoolEntities class Departments. Code First uses this property to discover and pull in any referenced types. If the type of the primary key property is numeric or GUID it will be configured as an identity column.
Every object can have a navigation property for every relationship in which it participates. Navigation properties allow you to navigate and manage relationships in both directions, returning either a reference object if the multiplicity is either one or zero-or-one or a collection if the multiplicity is many.
Code First infers relationships based on the navigation properties defined on your types. In addition to navigation properties, we recommend that you include foreign key properties on the types that represent dependent objects.