C# Multi Threading & Locking

Hi,

I have a Security object that contains two variables of type List<Price>, called CurrentPrices and NextPrices.

The security object loops through the CurrentPrices variable doing various calculations. Whilst this is being done I plan to use the ThreadPool to populate the NextPrices with data from a database.

Once the security object has finished looping through the CurrentPrices variable I copy the data from NextPrices to CurrentPrices and then NextPrices will again populate itself with fresh data whislt the security object loops through the CurrentPrices variable.

My question is how do I make sure that NextPrices has finished running before I copy its data to CurrentPrices. Please see the code below, I have stripped out some of the code to make it easier to follow as its not written to well as you can see!

Any help would be great,
Thanks,
M

public class Security
        {
            private delegate void delMultiThreadTP(Object Obj);
            private delMultiThreadTP delMultiTP;
            private int _LookBack;
            private AccessDataBank _Database;
            private ManualResetEvent _donePrice;
            private ManualResetEvent _doneFXPair;
            private DateTime _dtStart, _dtEnd;                        
            private SecurityTimeFrame[] _SecTP;
            private List<Price> _PricesNext = new List<Price>();
            private List<Price> Prices = new List<Price>();
            private string _Name;
            public string Signal{get;set;}

            private void RunTimePeriod(Object Obj)
            {
                ManualResetEvent[] doneTP = new ManualResetEvent[_SecTP.Length];

                // run through all the time periods
                for (int i = 0; i <= _SecTP.Length; i++)
                {
                    doneTP[i] = new ManualResetEvent(false);
                    _SecTP[i].RunTimePeriodSetup(doneTP[i]);
                    ThreadPool.QueueUserWorkItem(_SecTP[i].RunIndicatorDelegate, Prices);
                }

                WaitHandle.WaitAll(doneTP);

                // remove price oldest price element
                Prices.RemoveAt(0);
                
                // maybe i should be using an event here?
                if (CopyNextPriceList() == true)
                {
                    // need to copy prices over & then get next batch of prices
                    CopyPricesOver();
                   // start a new thread and repopulate _PricesNext using the GetPrices method below
                }

                _doneFXPair.Set();
            }

            private Boolean CopyNextPriceList()
            {
                Boolean Copy = false;
                if (Prices.Count < _LookBack)
                    Copy = true;                
                return Copy;
            }

            private void CopyPricesOver()
            {
                // Guessing I need to have some lock here??
                Prices.Clear();
                Prices.AddRange(_PricesNext.ToArray());
                _PricesNext.Clear();
            }

            private void GetPrices()
            {
                  _PricesNext = _Database.PriceData(_Name, _dtStart, _dtEnd);
            }
        }

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        public class Price
        {
            public DateTime dtDTime;
            public double BidOpen, BidHigh, BidLow, BidClose;
            public double AskOpen, AskHigh, AskLow, AskClose;
            public double MidOpen, MidHigh, MidLow, MidClose;
        }

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