What is the most efficient way to convert a std::vector to a .NET List?

Answer 1

If you're really that concerned about it, use unverifiable code instead:

List<unsigned>^ MethodA()
{
    std::vector<unsigned> const& runList = mpChannelNode->runList();
    array<unsigned>^ ret = gcnew array<unsigned>(runList.size());
    if (runList.size())
    {
        pin_ptr<unsigned> dest = &ret[0];
        std::memcpy(dest, &runList[0], runList.size() * sizeof(unsigned));
    }
    return gcnew List<unsigned>(ret);
}

That said, I'd be surprised if there was a noticeable difference either way...

Answer 2

I am not familiar with C++-CLI but one small improvement you can make is to create your list with the right capacity from the beginning.

List<UInt32> list = gcnew List<UInt32>(runList.size());

Another improvement would be to pre-increment your C++ iterator instead of post-incrementing it because currently you create an extra object for every element that is discarded immediately.

Answer 3

Consider turning into the vector directly into an array .. the below will work and be valid, until you resize the vector.

vector vec(10); int *array = &vec[0];

Then, you should be able to treat that (I think -- VS not on machine) as a passed array to populate your list.

You should also create your list with a size that you expect to need -- adding one by one will be slow.