How to store an array of elements, each element of which consists of 2 elements associated with it?

Question

C++ / C#

Good afternoon. A file comes to the program, it consists, for example, of the lines ala:
login1; password1
login2; password2
login3; password3
login4; password4
You need to put these lines into a dynamic array so that each element of this array contains 2 separate cells, with a login and a password, for example like this:
array[0][0] //login1
array[0][1] //password1
array[1][0] //login2
array[1][1] //password2
array[2][0] / /login3 array
[2][1] //password3
such array cells can be 2-3-4 thousand.
It only comes to mind to create a collection of structures with this data. But it seems to me that creating several thousand structures and calling them would be expensive.
Thank you.