When Should You Use ICollection for Many-to-Many/One-to-Many Relationships in EF Core?

Why Implement ICollection for Many-to-Many/One-to-Many Relationships in Entity Framework Core?

One commonly observed practice in Entity Framework tutorials is the use of ICollection as the type for navigation properties representing many-to-many or one-to-many relationships. Exploring the rationale behind this choice, the question arises:

Is ICollection mandatory for Entity Framework Core?

No, ICollection is not a strict requirement for Entity Framework Core. Instead, the appropriate interface depends on the intended use:

• IEnumerable: Allows iterating through a sequence of objects. Suitable for scenarios where only reading is required.
• ICollection: Supports iteration and modification, making it ideal for collections that need to be updated.
• List: A specialized ICollection implementation providing additional functionalities like sorting, indexing, and direct modification.

Purpose of Using ICollection

In the context of Entity Framework Core, ICollection plays a crucial role for many-to-many/one-to-many relationships due to lazy loading:

• By default, navigation properties are dynamically proxied, which requires the "many" end of a relationship to implement ICollection.
• This virtual type enables change tracking and proxies the navigation property, ensuring that any changes made are automatically tracked and persisted by Entity Framework Core.

In summary, while ICollection is not mandatory for all scenarios, it is essential for enabling lazy loading within many-to-many/one-to-many relationships in Entity Framework Core. Choosing the appropriate interface depends on the specific requirements for accessing, modifying, and persisting the underlying collection.

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