How to debug an empty LINQ result query?

Question

I've added a query to my repository, that queries for a list of orders that match the email search key. But when I step through the method, my result is null although the email string matches the email stored in my orders database document, "email": "brianvarley@gmail.com"

I'm using the MongoDB.Net driver to communicate with the MongoLabs repository. My other queries to query all documents works so doesn't seem to be a connection issue.

I tried hovering over c.Email, to check the database result, but no values pop up.

Does anyone know how I can debug the null result further?

This is the method that queries orders by email:

    public async Task<List<OrderModel>> GetAllByEmailAsync(string email)
    {
        if (orderList == null)
            await LoadDbAsync();
        return orderList.Where(c => c.Email == email).ToList();
    }

I added a dump to check orderList contents, but that shows a count = 0:

string dump = string.Join(",", orderList.ToString());

This is the LoadDBAsync(), when I step through the code, this method is skipped as OrderList isn't null:

    public async Task LoadDbAsync()
    {
        var orderCollection = StartConnection();

        try
        {
            orderList = await orderCollection.Find(new BsonDocument()).ToListAsync();

        }
        catch (MongoException ex)
        {
            //Log exception here:
            MessageBox.Show("A connection error occurred: " + ex.Message, "Connection Exception", MessageBoxButton.OK, MessageBoxImage.Warning);
        }
    }

And the StartConnection() called from LoadDbAsync:

    public IMongoCollection<OrderModel> StartConnection()
    {

        var client = new MongoClient(connectionString);
        var database = client.GetDatabase("orders");
        //Get a handle on the customers collection:
        var collection = database.GetCollection<OrderModel>("customer_orders");
        return collection;
    }

Answer 1

If your list isn't null but is empty, it will never return anything... Change your code for:

public async Task<List<OrderModel>> GetAllByEmailAsync(string email)
{
    if (orderList == null || orderList.Count() == 0)
        await LoadDbAsync();
    return orderList.Where(c => c.Email == email).ToList();
}