从数据库中的对象检索数组或列表

Question

I'm having trouble when I pull an object from the database with getting the framework to also get an an array in the object as well. I found that for sub objects the .Include("subobject") seems to work, but I can't get it to work for arrays or lists.

My Model:

public class RunData
{
   [Key]
   [Required]
   public int id { get; set; }
   public List<RunElement> Runs { get; set; }
   public string[] DataLabels { get; set; }
}

List of Entities:

public class ProgramEntities:DbContext
{
    public DbSet<RunData> RunData { get; set; }
    public DbSet<RunElement> RunElement { get; set; }
}

Controller Code:

    public ViewResult Details(int id)
    {
        RunData rundata = (from RunData in db.RunData.Include("Runs").in where RunData.id == id select RunData).First();
        return View(rundata);
    }

I did have all kinds of trouble with it not returning the list of Runs objects, but when I did the .Include("Runs") that fixed the problem. So, now my trouble is the DataLabels string array. If I try .Include("DataLabels") the program fails and says:

A specified Include path is not valid. The EntityType 'Program_Dataviewer.Models.RunData' does not declare a navigation property with the name 'DataLabels'.

I have searched online some, I'm not seeing any clear cut answers. Thank you for the help.

Answer 1

You can not have collections of primitives in your data model, since each collection must be mapped to a table in the relational space (think about it - how is the database going to organize/save your collection?). What you can do is introduce a table / entity for DataLabels , eg something like this:

public class RunData
{
   [Key]
   [Required]
   public int id { get; set; }
   public List<RunElement> Runs { get; set; }
   public List<DataLabel> DataLabels { get; set; }
}

public class DataLabel
{
  [Key]
  public int id { get; set; }
  public string LabelName { get; set; }
}