Lightspeed 3 composite keys

Ok simple question is: how does this work? unsure of the semantics for setting up composite primary keys, any help?

Define a struct to represent the type of the key, then inherit from Entity<MyKeyType>.  For example, here's an entity with a composite key consisting of a ProductId and a LanguageId:

public struct InternationalProductId
{
  private readonly int _productId;
  private readonly string _languageId;

  public InternationalProductId(int productId, string languageId)
  {
    _productId = productId;
    _languageId = languageId;
  }

  public int ProductId
  {
    get { return _productId; }
  }

  public string LanguageId
  {
    get { return _languageId; }
  }

  public override bool Equals(object obj)
  {
    if (obj is InternationalProductId)
    {
      InternationalProductId other = (InternationalProductId)obj;
      return other.ProductId == ProductId && StringUtils.EqualsIgnoreCase(other.LanguageId, LanguageId);
    }
    else
    {
      return false;
    }
  }

  public override int GetHashCode()
  {
    return 29 * ProductId.GetHashCode()
      + (LanguageId == null ? 0 : LanguageId.GetHashCode());
  }

  public override string ToString()
  {
    return ProductId.ToString() + "/" + LanguageId;
  }
}

public class InternationalProduct : Entity<InternationalProductId>
{
  private string _description;

  public string Description
  {
    get { return _description; }
    set { Set(ref _description, value, "Description"); }
  }
}

thanks Ivan, is there any support for this in the lightspeed designer in 3 or does it have to be a hand coded entity? Cheers Owen

Yes, it is supported in the designer.

If you are doing database-first, which is our assumed scenario for composite keys, then dragging a table with multiple primary keys onto the design surface will create multiple identity properties.

If you are doing model-first, our first recommendation is of course not to use composite keys!  But if you really need to do CKs in a model-first scenario, then you will need to go to the LightSpeed Model Explorer, locate the entity in the tree view, right-click and choose Add New Identity Property.  (Once you've put an entity into "composite key mode" by doing this, you can skip this little dance and right-click on the entity surface to add further keys.)

In both cases, this will result in generating a struct called XxxId (where Xxx is the name of the entity) and declaring the entity type as Entity<XxxId>.  Note that we do NOT generate overrides for Equals and GetHashCode so you may want to add overrides for these via the partial class.