When I use resize(int newsize) in C++ for vector, it means that the size of this vector are set to newsize
resize(int newsize)
vector
size
newsize
Setting List<T>.Capacity is like using std::vector<T>.reserve(..). Maybe List<T>.AddRange(..) fit your needs.
List<T>.Capacity
std::vector<T>.reserve(..)
List<T>.AddRange(..)