How do you handle relationships to other tables with PetaPoco? - petapoco

Question

As an example, if I have a POCO for Forum and one for ForumPost, how can I elegantly return a list of ForumPosts and specify this right in the model. I'm doing it manually now by adding my db.Query call directly in the List property, but is there a better way?
[TableName("Forum")]
[PrimaryKey("ForumID")]
[ExplicitColumns]
public class Forum : BaseModel
{
[Column]
public int ForumID { get; set; }
[Column]
public string ForumName { get; set; }
[Column]
public string ForumDescription { get; set; }
[ResultColumn]
public List<ForumPost> {
get
{
// return list of ForumPost - what's a good way to handle this?
}
}
}

Answer 1

I wrote an static extension to this, so I can set this in my property like this (using some of my classes). This property would be in your POCO model:
private List<AssessmentAssignment> _AssessmentAssignments;
[ResultColumn]
public List<AssessmentAssignment> AssessmentAssignments
{
get
{
return ServiceExtensions<AssessmentAssignment>.GetRelatedList(this.GetType());
}
set
{
_AssessmentAssignments = value;
}
}
Here is the ServiveExtension that I wrote up to do it, but not sure i like this yet. It works, but meh. Anyone have any better ideas?
public static class ServiceExtensions<T> where T : class, new()
{
/// <summary>
/// Experimental way to retrieve a foreign key related list with PetaPoco
/// </summary>
/// <param name="PrimaryTableType"></param>
/// <returns></returns>
public static List<T> GetRelatedList(Type PrimaryTableType)
{
var primaryTableData = PocoData.ForType(PrimaryTableType);
var relationshipTableData = PocoData.ForType(typeof(T));
using (PetaPoco.Database db = new PetaPoco.Database("ConnStringName"))
{
PetaPoco.Sql sql = new PetaPoco.Sql("SELECT A.* FROM " + relationshipTableData.TableInfo.TableName + " A")
.Append("JOIN " + primaryTableData.TableInfo.TableName + " B ON A." + primaryTableData.TableInfo.PrimaryKey + " = B." + primaryTableData.TableInfo.PrimaryKey);
return db.Fetch<T>(sql);
}
}
}