Dictionary in MultiThreaded Application (memory management?)

Question

I have a Dictionary that is Dictionary<int, RSendPacket> _Packets and there are two main threads. Thread #1 adding packets with this function

public void EnqueueOutgoingData(int id, byte[] data)
{
    RSendPacket packet = new RSendPacket(data);
    _Packets.Add(id, packet);
}

The Thread #2 is reads and sends the packet via socket like this

private void _Process(RSendPacket packet)
{
    foreach (KeyValuePair<int, RSendPacket> o in _Packets)
    {
        //Socket send (o.Value >> That's RSendPacket class)
    }
}

at this point, I'm getting an error. I'm adding "asdf" but it carries it as "► o". It is a threading/memory error I think but I cant fix it because I don't know how! Can anybody help me about this? (I can implement a system in C++ with pointers and memory management and it should be a memory management problem -caused by my bad c#)

EDIT1: And yes there isn't a thread-safe implemention but I've tried it with 'lock()' and not works!

EDIT2: Oh another important edit. I'm using C# 2.0 with Unity. So solution should be a C# 2.0 (mono) code :/

Where do you see the "corrupted" value? In the `_Process` method? If you only queue and process a single packet does that work? (I'm thinking this would rule out multi-threading issues in determining the cause of the corruption.) — richaux, Feb 15 '14 at 15:43
Also, at what point do you remove the sent packet from the `_Packets` collection? ... and is the `packet` passed in to `_Process` of any significance? — richaux, Feb 15 '14 at 15:47

score 0 · Answer 1 · answered Feb 15 '14 at 15:28

0

Looks like you might want to use a queue for this kind of operation, it fits better what you are trying to do.

If you experience concurrency issues, you can use the ConcurrentQueue class.

answered Feb 15 '14 at 15:28

Andrea

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It must be a dictionary because I need to find my values with a id key. – PilawyerDev Feb 15 '14 at 15:32
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In your example you are iterating through the keyValuePairs and sending the value only - please update your code with relevant details about how you are using the dictionary to get better advice! – Andrea Feb 15 '14 at 15:35

score 0 · Answer 2 · answered Feb 15 '14 at 15:33

0

You don't have to use a lock to keep it thread safe. simply use ConcurrentDictionary in place of the regular dictionary.

answered Feb 15 '14 at 15:33

i3arnon

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And it works but this is not the solution that I'm looking for because of C# 2.0 :) – PilawyerDev Feb 16 '14 at 11:06

score 0 · Answer 3 · answered Feb 15 '14 at 15:34

A Dictionary<TKey, TValue> is not thread-safe, so behavior is undefined in your multi-threaded example. Also, the order in which items are returned when iterating over a Dictionary<TKey, TValue> is undefined, so you might not get what you expect even if you use a ConcurrentDictionary<TKey, TValue> or implement your own locking.

score 0 · Accepted Answer · edited May 23 '17 at 12:06

0

The real solution (I've tried and that works) is l3arnon's answer but I'm going to implement this system in C# 2.0 and I've implemented it like this method with Monitor.

edited May 23 '17 at 12:06

Community

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answered Feb 16 '14 at 11:06

PilawyerDev

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Dictionary in MultiThreaded Application (memory management?)

4 Answers4