Using IList, List, ICollection for 1 to n relationships in EF Core

Question

What is the best practice to define a One-to-Many relationship in EF Core?

Is it recommended to generally use lists, as these offer more functionalities? Then rather the interface IList instead of List, as it does not define the implementation? If it does matter, on what criteria should I pick one or the other?

Microsoft suggests the following https://learn.microsoft.com/en-us/ef/core/modeling/relationships

public class Blog
{
    public int BlogId { get; set; }
    public List<Post> Posts { get; set; }
}

public class Post
{
    public int PostId { get; set; }
    public int BlogId { get; set; }
    public Blog Blog { get; set; }
}

Whereas

http://www.entityframeworktutorial.net/efcore/configure-one-to-many-relationship-using-fluent-api-in-ef-core.aspx

https://www.learnentityframeworkcore.com/configuration/one-to-many-relationship-configuration suggest ICollections

Is the following answer of 2011 still valid in EF Core?

https://stackoverflow.com/a/7655974/10148774

Answer 1

The decision you should choose will depend on which operations you need to execute.

In general, you have three main options:

• IEnumerable<> for a list of objects that only needs to be iterated through (no aditional operations like modification).
• ICollection<> for a list of objects that needs to be iterated through and modified.
• List<> for a list of objects that needs to be iterated through, modified, sorted, access by index...

Now you can think: So I will always use List because it provides the most functionality, but keep in mind that it has the most overhead and a good object-oriented practice is to program towards the interface and not the implementation. Implementations can and will change.

Then you need to balance and analyze your specific scenario to make the best choice.

Regards,