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Editorial Team
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Asked: 2026-06-14T18:13:11+00:00

Given the opportunity to rewrite, I would, but anyway, the code as it stands:

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Given the opportunity to rewrite, I would, but anyway, the code as it stands:

List<string> foobar;

Then we add a bunch of strings to foobar.

At count=16777216, we hit an out of memory limit.

My understanding is that each string would be a different size. Indeed looking at the data (not my data), most are 2 or 3 characters.

what is the max limit of data into list in c#? indicates that the max limit is:

The maximum number of elements that can be stored in the current
implementation of List is, theoretically, Int32.MaxValue – just
over 2 billion.

However:

In the current Microsoft implementation of the CLR there’s a 2GB
maximum object size limit. (It’s possible that other implementations,
for example Mono, don’t have this restriction.)

In my example, I have, what, 16 million results * a few bytes? Task manager shows about a gig being used, but I have 8 gigs of RAM.

16777216 (2^24) seems like a fairly specific value – suspiciously like a limit, but I can’t find any documentation anywhere to a) back this up or b) find a way around it?

Any help would be appreciated.

Some code:

List<string> returnList = new List<string>();
SqlDataReader dr; //  executes a read on a database, have removed that part as that bit works fine

  if (dr.HasRows)
  {
      while (dr.Read())
      {
          returnList.Add(dr.GetString(0).Trim());
      }
  }

That’s the simplified form, I now have some try/catch for the OOM Exception, but this is the actual code that’s giving me grief.

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1 Answer

  1. Editorial Team

    If you’re trying to use very large lists in 64 bit environments you need to enable large objects in the application configuration.

    http://msdn.microsoft.com/en-us/library/hh285054.aspx

    The OOM is likely due to the way Lists/ArrayLists allocate memory, which I believe is each time their boundary is reached, they attempt to double in size. The list cannot double from 2^24. You could theoretically maximize your list size by pre-specifying a size. (I.e. 2GB)

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