How would that make it any less efficient? As long as the contents
aren't changing occasionally (so that locking is an issue) then a deep-
clone can only add time.
Technically, I belive a string[] is marginally quicker than a
List<string>, so perhaps swap for that? However - better is to look at
a profiler and see where your time is really going. On a string[], I
believe (IIRC) indexer access is again /marginally/ quicker - but your
own tests may help.

Marc

Not if you create a new copy each time you need to loop over it.  That
would obviously just make things slower, because you'd iterate the list
twice instead of just once.

However, if you make the list essentially immutable, only replacing it
if and when it needs to be changed by some other part of your
architecture, then you should be able to have as many threads reading
simultaneously from the list as you like without any problems and
without having to create any copies of the list.

Make the reference itself volatile, initialize a new version when
necessary, and just assign the reference to the new version when it's
been completely initialized.

Less efficient than what?  How?  Yes...all you are doing is copying the
reference to the list from one variable or property to the other
variable.  It seems to me that should be very efficient.  Vastly more
efficient than cloning, deep or otherwise, the entire list.

In what way would cloning be better?

If you're only processing 2000 requests per second, you may not be
putting enough load on the system to note significant differences
between designs.  Maybe try increasing the load until you reach the
maximum throughput for a given design.  Then you can modify the design
and see if things get better or worse, by testing the system again to
maximum load and seeing whether the new maximum load is different from
the previous one, and by how much.

Pete

How long is the list? I wouldn't expect iterating over a list 2000
times a second would be significant in terms of performance unless it's
really pretty long.

For instance, here's code to iterate over a list of 10000 entries,
20000 times. On my laptop (which is far from "server class") it takes
about 3 seconds. That's actually longer than I expected, but then 10000
is quite a long list. How long is your actual list?

using System;
using System.Collections.Generic;
using System.Diagnostics;

public class Test
{
   static List<string> list = new List<string>();
   
   const int Iterations = 5000;
   
   static void Main()
   {
       for (int i=0; i < 10000; i++)
       {
           list.Add(i.ToString());
       }
       
       int total=0;
       Stopwatch sw = Stopwatch.StartNew();
       for (int i=0; i < Iterations; i++)
       {
           foreach (string x in list)
           {
               total += x.Length;
           }
       }
       Console.WriteLine(sw.ElapsedMilliseconds);
       Console.WriteLine(total);
   }
}

Thanks for the tip. I'll look into it.

I should have detailed that, it's a short list, most the time under 20, but
could grow to 1000.

The entire page should never toke more than 100 mil seconds to complete
worse case, the process in the loop take 70% of the processing time of the
entire page.

The list is never altered by code in the page. There is a single thread
timer background process that builds a tempory list from the db, once built,
it locks the entire static object and replaces the old object with a new one
object which contains the new list. (oldStaticObj = tempNewObj) This happens
every 2 seconds.

Thank you all for your continuing helpful feedback.

What exactly are you doing when you loop over the list?  Can you cache
the results of the loop and just use that or do you really need to
loop through the items in every request, 2000 times a second?  Or is
there another collection that would be more efficient.. are you
looking for an item? can you use a dictionary? Would sorting the list
allow you to loop differently and skip items?

HTH,

Sam

------------------------------------------------------------
We're hiring!  B-Line Medical is seeking .NET
Developers for exciting positions in medical product
development in MD/DC.  Work with a variety of technologies
in a relaxed team environment.  See ads on Dice.com.