Question

I want to see the System.OutOfMemoryException and the memory consumed in the task manager, when the app is built against x64. There are two drop-downs in the Build tab in the app properties: “Platform target” and “Platform”, both are set to x64.

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            List<long> lst = new List<long>();
            while (true)
            {
                lst.Add(long.MaxValue);
            }
        }
    }
}

It is indeed showing OutOfMemoryException…but when it stops, the task manager is showing a number like 1587443K which is 1.5GB which would I expect if it was built against x86.
Yes, the operating system is 64bit.

Am I forgetting something else?

Answer 1

Am I forgetting something else?

Yes – in .NET 4, there was still a 2GB-per-object limit. (You could use much more memory, but not in a single object.) I suspect your list needs to reallocate its internal buffer, requiring ~3GB in a single array.

You may be pleased to hear that .NET 4.5 supports larger objects if you set the <gcAllowVeryLargeObjects> configuration parameter.