Entity Framework and Models with Simple Arrays

Question

This is my model class.

public class Lead
{
    private readonly ObservableCollection<String> m_tags = new ObservableCollection<string>();

    public int LeadId { get; set; }
    public string Title { get; set; }
    public ObservableCollection<String> Tags { get { return m_tags; } }

}

Does Entity Framework offer a way to represent this using either Model-First or Code-First?

EDIT: I'm looking for a way to do this without changing the public API of the model. The fact that there is some sort of Tags table shouldn't be visible to the downstream developer.

BrokenGlass · Accepted Answer · 2011-05-04 01:03:32Z

4

Since your model has to be represented in a relational way, you can only use primitive types (that have an equivalent in a SQL DB) or other entities within a entity definition - that means the tags are represented by their own entity. In your case it would be something like this using Code first approach:

public class Lead
{
    public int LeadId { get; set; }
    public string Name { get; set; }
    public virtual ICollection<Tag> Tags { get; set; }
}

public class Tag
{
    public int TagId { get; set; }
    public string Name { get; set; }
}

public class SomeContext : DbContext
{
    public DbSet<Lead> Leads { get; set; }
    public DbSet<Tag> Tags { get; set; }
}

This (by default) will be represented in the database as a table Leads, a table Tags, and a relationship table LeadTags that only contains {LeadId, TagId} pairs.

answered May 4, 2011 at 1:03

BrokenGlass

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4 Comments

Jonathan Allen Over a year ago

I understand that I need a table to hold the tags, but is there is any way to avoid leaking that into the model?

BrokenGlass Over a year ago

@Jonathan: Not as far as I know - but your view-model can (and probably should) certainly be separate from the entity data model, you could do the mapping in between.

Jonathan Allen Over a year ago

True. But at that point I might as well throw away EF and use straight stored procedures. The whole point of having an ORM is so that we don't need to map from the resultset to the model.

BrokenGlass Over a year ago

@Jonathan: Sorry I didn't have better news - I hear primitive arrays in models are supported in NHibernate though - maybe that is an alternative for your project?

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