Exception of type 'System.OutOfMemoryException' was thrown

c# c#-4.0 ef-code-first entity-framework sql-server


Basically I use Entity Framework to query a huge database. I want to return a string list then log it to a text file.

List<string> logFilePathFileName = new List<string>();
var query = from c in DBContext.MyTable where condition = something select c;
foreach (var result in query)
    filePath = result.FilePath;
    fileName = result.FileName;
    string temp = filePath + "." + fileName;
    if(logFilePathFileName.Count %1000 ==0)

However I got an exception when logFilePathFileName.Count=397000. The exception is:

Exception of type 'System.OutOfMemoryException' was thrown.

A first chance exception of type 'System.OutOfMemoryException' occurred in System.Data.Entity.dll


What I want to use a different query say: select top 1000 then add to the list, but I don't know after 1000 then what?

1/30/2013 2:40:47 PM

Accepted Answer

Most probabbly it's not about a RAM as is, so increasing your RAM or even compiling and running your code in 64 bit machine will not have a positive effect, in this case.

I think it's related to a fact that .NET collections are limited to maximum 2GB RAM space (no difference either 32 or 64 bit).

To resolve this, split your list to much smaller chunks and most probabbly your problem will gone.

Just one possible solution:

foreach (var result in query)
    if(logFilePathFileName.Count %1000 ==0) {
        logFilePathFileName = new List<string>(); //RESET LIST !|


If you want fragment a query, you can use Skip(...) and Take(...)

Just an explanatory example:

var fisrt1000 = query.Skip(0).Take(1000);
var second1000 = query.Skip(1000).Take(1000);

... and so on..

Naturally put it in your iteration and parametrize it based on bounds of data you know or need.

1/30/2013 3:16:46 PM

Popular Answer

Why are you collecting the data in a List<string> if all you need to do is write it to a text file?

You might as well just:

  • Open the text file;
  • Iterate over the records, appending each string to the text file (without storing the strings in memory);
  • Flush and close the text file.

You will need far less memory than now, because you won't be keeping all those strings unnecessarily in memory.

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