[Cosmos] Support collections of scalar types

[Chiliyago]

An entity class with a property of List or ICollection of Int does not work.

public class Foo
 {
     public ICollection<int> RowValues { get; set; }
     public ICollection<int> ColValues { get; set; }
 }

Here is the error message.
The property 'RowValues' on entity type 'Models.Foo' has not been added to the model or ignored.

Is this a bug or am I doing this wrong?

Thanks

[rowanmiller]

EF doesn't support storing collections of scalar types. The best workaround at the moment would be to add [NotMapped] to those properties and then have another property that wraps the ICollection<int> represents the serialized for of the data (such a comma-separated string). Then let EF map to that property.

[bjorn-ali-goransson]

Any tips on how I could configure EF Core to always map IEnumerable<int> to string and the value stored to DB will be its JSON representation?

I.e. custom mapping, serializing and parsing based on type (that is, general - not based on property per se).

[ajcvickers]

Note: there are two potential approaches to solving this problem:

• Using a value converter to serialize all the values into a single column
• Mapping to a table which contains the values and collapsing that mapping down to the IEnumerable/ICollection property on the entity. (See OwnsMany primitive type support? #14115)

We may choose to implement either one or both of these. The first can be done manually without mich code using a custom value converter. For example:

modelBuilder
    .Entity<User>()
    .Property(e => e.Roles)
    .HasConversion(
        v => string.Join(',', v),
        v => v.Split(',', StringSplitOptions.None));

(Note that this is a naive serialization that doesn't account for the separator character being included in some of the values, but using something more robust, such as JSON serialization, is just a matter of plugging in the right serialization code.)

[roji]

#29427 already tracks mapping primitive collections to JSON columns, whereas #25163 tracks mapping primitive collections to a separate table. Is this issue needed (though it's a ancient 4-digit issue which deserves respect!)