Unable to get Item from SQLite.Net Async PCL - xamarin

Question

I am struggling to get an Item by ID using the asynchronous API of SQLite.Net Async PCL. Here is my model class
public class Invoice : IEntityBase
{
public Invoice()
{
LineItems = new List<LineItem>();
DateCreated = DateTime.Now;
}
[PrimaryKey, AutoIncrement, Column("_id")]
public int Id { get; set; }
public DateTime DateCreated { get; set; }
public int Term { get; set; }
public bool Paid { get; set; }
public decimal Total { get; set; }
public string Notes { get; set; }
[OneToMany(CascadeOperations = CascadeOperation.All)]
public List<LineItem> LineItems { get; set; }
}
And the LineItems that has a One to Many relationship here
[PrimaryKey, AutoIncrement, Column("_id")]
public int Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public decimal Price { get; set; }
public string Category { get; set; }
public int Qty { get; set; }
[ForeignKey(typeof(Invoice))]
public int InvoiceId { get; set; }
[ManyToOne]
public Invoice Invoice { get; set; }
Here is the constructor:
public SQLiteAsyncConnection DbConnection;
public InvoiceDatabase(ISQLitePlatform platform, string databasePath)
{
if (DbConnection == null)
{
var connectionAsync = new Func<SQLiteConnectionWithLock>(() =>
new SQLiteConnectionWithLock
(
platform,
new SQLiteConnectionString(databasePath, false)
)
);
DbConnection = new SQLiteAsyncConnection(connectionAsync);
DbConnection.CreateTableAsync<Invoice>();
DbConnection.CreateTableAsync<LineItem>();
}
}
Other CRUD methods (Insert, GetALL) is working except getting an Invoice by ID, and both Visual Studio and Xamarin Studio are not giving me any useful stacktrace.
Here is the Get Method
private readonly InvoiceDatabase _database;
public InvoiceRepository(ISQLitePlatform platform, string databasePath)
{
if (_database == null)
{
_database = new InvoiceDatabase(platform, databasePath);
}
}
public async Task<Invoice> GetInvoice(int id)
{
var result = await _database.DbConnection.Table<Invoice>()
.Where(t => t.Id == id)
.FirstOrDefaultAsync();
return result;
}
I am passing in the Android implementation of SQLite, and like I said the Database is created but I am unable to get the Invoice object back, I even tried
public Task<Invoice> GetInvoiceWithChildren(int id)
{
return _database.DbConnection.GetWithChildrenAsync<Invoice>(id);
}
Any Help will be greatly appreciated.

Answer 1

After three days of chasing shadows it turned out that it is just a very simple thing that is tripping me up. I am tying to save a List of objects like so
[OneToMany(CascadeOperations = CascadeOperation.All)]
public List<LineItem> LineItems { get; set; }
I missed the part of the documentation that repeats the fact that SQLite.Net is a lightweight ORM - that point could not be stressed enough so you will have to remove your full size ORM hats such EF. So after reading from the SQLite-Net Extension documentation which says
Text blobbed properties
Text-blobbed properties are serialized into a text property when saved and deserialized when loaded. This allows storing simple objects in the same table in a single column.
Text-blobbed properties have a small overhead of serializing and deserializing the objects and some limitations, but are the best way to store simple objects like List or Dictionary of basic types or simple relationships.
I change my proptery like so and everything is now working as expected. Off now to dealing with the nuances of Async and Await
[TextBlob("LineItemBlobbed")]
public List<LineItem> LineItems { get; set; }
public string LineItemBlobbed { get; set; }