Relationship mapping attributes, which can be used an alternative to the model building API for some aspects of relationship configuration.- Hi, this is Steve Wright, welcoming you to this week's Nuke Nugget: How to View a Wireframe Object Over Its 2D Clip.Relationship conventions, which discover entity types, their properties, and the relationships between the types.To find out more about other options, see: Most of the examples show the model building API. Relationship navigations, which describes how navigations are layered over a foreign key to provide an object-oriented view of the relationship.ĮF models are built using a combination of three mechanisms: conventions, mapping attributes, and the model builder API.Foreign and principal keys in relationships, which covers how foreign keys map to the database.To dig deeper into the properties of entity types involved in relationship mapping, see: If you are new to EF, then trying the examples linked in in the bullet points above is a good way to get a feel for how relationships work. Many-to-many relationships, in which any number of entities are associated with any number of other entities.One-to-one relationships, in which a single entity is associated with another single entity.One-to-many relationships, in which a single entity is associated with any number of other entities.To jump into examples for different kinds of relationships, see: Find out moreĮF supports many different types of relationships, with many different ways these relationships can be represented and configured. Now all these properties will behave coherently together as a representation of a single relationship between Blog and Post. For example: protected override void OnModelCreating(ModelBuilder modelBuilder) This is done automatically by EF when building a simple relationship like this, but can also be specified explicitly when overriding the OnModelCreating method of your DbContext. The primary key property of Blog, Blog.Id, and the foreign key property of Post, Post.BlogId, can then be associated with the references ("navigations") between the entity types ( Blog.Posts and Post.Blog). However, even when the properties are hidden, it is important to recognize that they still exist in the EF model. Primary and foreign key properties don't need to be publicly visible properties of the entity type. Once this mapping is made, EF changes the foreign key values as needed when the references between objects change, and changes the references between objects as needed when the foreign key values change.
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