Here's piece of code where It throws the exception sometimes:
Pendings = ClientCode.PendingOrders.Select(x => new DisplayPending()
{
ItemCode = ClientCode.Items.First(y => y.Id == x.ItemCode).Id,
ItemName = ClientCode.Items.First(y => y.Id == x.ItemCode).Name,
OrderNo = x.BuyOrderNo == 0 ? x.SellOrderNo : x.BuyOrderNo,
OrderType = x.OrderType == OrderType.Buy ? "Buy" : "Sell",
PartyCode = x.PartyCode,
Price = x.Price,
Quantity = x.Quantity
});
and here's the message:
System.NullReferenceException: 'Object reference not set to an instance of an object.'
x was null.
PendingOrders is anObservableCollection and It has more than 500 items.
EDIT
Here's how I populate my extended ObservableCollection:
public class AsyncObsetion<T> : ObservableCollection<T>
{
SynchronizationContext context = SynchronizationContext.Current;
readonly object _lock = new object();
public AsyncObsetion() { BindingOperations.EnableCollectionSynchronization(this, _lock); }
public AsyncObsetion(IEnumerable<T> list) : base(list) { BindingOperations.EnableCollectionSynchronization(this, _lock); }
void RaiseCollectionChanged(object param) => base.OnCollectionChanged((NotifyCollectionChangedEventArgs)param);
void RaisePropertyChanged(object param) => base.OnPropertyChanged((PropertyChangedEventArgs)param);
protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
{
if (SynchronizationContext.Current == context) RaiseCollectionChanged(e);
else context.Send(RaiseCollectionChanged, e);
}
protected override void OnPropertyChanged(PropertyChangedEventArgs e)
{
if (SynchronizationContext.Current == context) RaisePropertyChanged(e);
else context.Send(RaisePropertyChanged, e);
}
public void InsertRange(IEnumerable<T> items)
{
this.CheckReentrancy();
foreach (var item in items)
this.Items.Add(item);
this.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
}
}
When Client connects to Server, it sends 6 byte[] which are added in 8 AsyncObsetion<T> named Items, NewsCollection, Issued, BuyOrders, SellOrders, PendingOrders, ExecutedOrders and MyExecutedOrders on client side. This piece of code is responible for handling those byte[] which client gets from server:
var tasks = new List<Task>();
tasks.Add(Task.Run(() =>
{
for (int i = 0; i < header.ItemSize; i += Constants.itemSize)
{
var item = PacMan<ItemStruct>.Unpack(itemArray.Skip(i).Take(Constants.itemSize).ToArray());
Items.Add(new Item()
{
Id = item.Id,
Name = item.Name,
Cap = item.Cap,
Floor = item.Floor,
Mid = item.Floor + ((item.Cap - item.Floor) / 2),
Securities = item.Securities,
Owners = item.Owners,
Govt = item.Govt,
Institutions = item.Institutions,
Foreign = item.Foreign,
Public = item.Public,
PerSecurity = PacMan<PerSecurityFinancialsStruct>.ArrayToList<PerSecurityFinancials>(item.PerSecurity),
Dividends = PacMan<DividendStruct>.ArrayToList<Dividend>(item.Dividends),
InitialSecurity = item.InitialSecurity
});
}
}).ContinueWith(t =>
{
if (header.HasExecuted) GetExOrders(header.ExecutedSize, execArray);
if (header.HasNews) AddNews(newsArray.ToArray());
}));
tasks.Add(Task.Run(() => { if (header.HasBuy) GetOrders(header.BuySize, buyArray, "buy"); }));
tasks.Add(Task.Run(() => { if (header.HasSell) GetOrders(header.SellSize, sellArray, "sell"); }));
tasks.Add(Task.Run(() => AddIssue(issueArray.ToArray())));
Task.WaitAll(tasks.ToArray());
hasReceivedData = true;
App.Current.Dispatcher.Invoke(() => CommandManager.InvalidateRequerySuggested());
OnConnected();
OrderVM.ItemCode = Items.First().Id;
e.Completed += Receive;
e.SetBuffer(headerBuffer, 0, headerBuffer.Length);
if (!e.AcceptSocket.ReceiveAsync(e)) Receive(null, e);
OnConnected() is an event and when it's fired client starts the process of creating Pendings out of PendingOrders, which is made out of buyArray and sellArray. I think here's the problem and I believe somehow OnConnected() gets fired before Task.WaitAll(tasks.ToArray()) sometimes. If someone is interested, here's what GetOrders does:
void GetOrders(int size, IEnumerable<byte> array, string type)
{
var orderList = new List<AllOrder>();
var pendingList = new List<AllOrder>();
for (int i = 0; i < size; i += Constants.orderSize)
{
var order = PacMan<AllOrderStruct>.Unpack(array.Skip(i).Take(Constants.orderSize).ToArray());
AddInitNewOrder(order, orderList, pendingList);
}
if (type == "buy") CheckNumberAndAdd(orderList, BuyOrders);
else CheckNumberAndAdd(orderList, SellOrders);
CheckNumberAndAdd(pendingList, PendingOrders);
}
here's AddInitNewOrder:
void AddInitNewOrder(AllOrderStruct order, List<AllOrder> orders, List<AllOrder> pendingOrders)
{
var o = new AllOrder();
o.Action = order.Action;
o.OrderType = order.OrderType;
o.ItemCode = order.ItemCode;
o.BrokerName = order.BrokerName;
o.PartyCode = order.PartyCode;
o.Price = order.Price;
o.Quantity = order.Quantity;
o.BuyOrderNo = order.BuyOrderNo;
o.SellOrderNo = order.SellOrderNo;
orders.Add(o);
if (o.BrokerName == BrokerName) pendingOrders.Add(o);
}
and here's CheckNumberAndAdd:
void CheckNumberAndAdd<T>(List<T> normList, AsyncObsetion<T> obsList)
{
var count = normList.Count;
if(count > 50)
{
obsList.InsertRange(normList.Take(count - 50));
var remaining = normList.Skip(count - 50).ToList();
for (int i = 0; i < remaining.Count; i++) obsList.Insert(0, remaining[i]);
}
else for (int i = 0; i < count; i++) obsList.Insert(0, normList[i]);
}
If I set brekpoint in GetOrders function, I see pendingList gets 483 items from sellArray and 494 items from buyArray, so altogether I've 977 items. So I should get 977 Items in PendingOrders always BUT If I remove brekpoint in GetOrders and set breakpoint in Subscribe method, which is hooked into that event ClientCode.OnConnected += Subscribe; I see PendingOrders sometimes gets less than 977 items.
