Unable to create a constant value of type (type) Only primitive types ('such as Int32, String, and Guid') are supported in this context

Question

I\'ve read ALL of:

• Unable to create a constant value of type 'System.Object' in Entity Framework

• Entity Framework - "Unable to

Answer 1

I think that EF is trying to convert where a.Photos.Contains(p) into SQL like WHERE p IN (a.Photos), but it doesn't know how to express a.Photos in SQL. The SQL you want probably looks like WHERE p.Id IN (1, 2, 3), so you could try doing that in C#:

static IQueryable VisiblePhotos(this Album a)
{
    var photoIds = a.Photos.Select(p => p.Id).ToArray();
    return from p in VisibleObjects.OfType() where photoIds.Contains(p.Id) select p;
}