/// <summary>
/// Gets open orders matching the specified filter. Specifying null will return an enumerable
/// of all open orders.
/// </summary>
/// <param name="filter">Delegate used to filter the orders</param>
/// <returns>All filtered open orders this order provider currently holds</returns>
public List <Order> GetOpenOrders(Func <Order, bool> filter = null)
{
filter = filter ?? (x => true);
return(_orderProcessor.GetOpenOrders(x => filter(x)));
}