Questions

What is many-to-many relationship in Entity Framework?

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What is many-to-many relationship in Entity Framework?

Entity Framework Many-to-Many Relationships. In a many-to-many relationship, each row of data in one table is linked to many rows in the second table and vice versa. A many-to-many relationship occurs when multiple records in one table are associated with multiple records in another table.

How do I create a many-to-many relationship in Entity Framework Core?

To add a many-to-many relationship in EF Core you need to:

  1. Create a linking entity class that has the foreign keys(s) of the two entities you want to form a many-to-many link between.
  2. It is efficient (but not necessary) to make these two foreign keys into the composite primary key.

What is ModelBuilder in MVC?

Provides a simple API surface for configuring a IMutableModel that defines the shape of your entities, the relationships between them, and how they map to the database. You can use ModelBuilder to construct a model for a context by overriding OnModelCreating(ModelBuilder) on your derived context.

How do you implement many-to-many relationships?

Junction table. When you need to establish a many-to-many relationship between two or more tables, the simplest way is to use a Junction Table. A Junction table in a database, also referred to as a Bridge table or Associative Table, bridges the tables together by referencing the primary keys of each data table.

What is OnModelCreating in Entity Framework?

The DbContext class has a method called OnModelCreating that takes an instance of ModelBuilder as a parameter. This method is called by the framework when your context is first created to build the model and its mappings in memory.

How do you create a many-to-many relationship?

To create a many-to-many relationship:

  1. Create a new table to serve as the intermediate table.
  2. Create a relationship between the new table and the existing tables.
  3. Add lookup fields to the relationship.
  4. Delete unnecessary fields from parent tables.
  5. Create automated email notifications for the new table.

Is OnModelCreating required?

OnModelCreating is not necessary, but at the same time will not hurt if called – that’s why Sometimes it’s there, sometimes not. Sometimes at the beginning of the method, other times at the end.

Where do you override OnModelCreating?

You can override the OnModelCreating method in your derived context and use the ModelBuilder API to configure your model. This is the most powerful method of configuration and allows configuration to be specified without modifying your entity classes.