what is difference between string array and list of string in c#

Question

Arrays are a lower level abstraction than collections such as lists. The CLR knows about arrays directly, so there's slightly less work involved in iterating, accessing etc.

However, this should almost never dictate which you actually use. The performance difference will be negligible in most real-world applications. I rarely find it appropriate to use arrays rather than the various generic collection classes, and indeed some consider arrays somewhat harmful. One significant downside is that there's no such thing as an immutable array (other than an empty one)... whereas you can expose read-only collections through an API relatively easily.

The article is from 2004, that means it's about .net 1.1 and there was no generics. Array vs collection performance actually was a problem back then because collection types caused a lot of exta boxing-unboxing operations. But since .net 2.0, where generics was introduced, difference in performance almost gone.

An array is not resizable. This means that when it is created one block of memory is allocated, large enough to hold as many elements as you specify.

A List on the other hand is implicitly resizable. Each time you Add an item, the framework may need to allocate more memory to hold the item you just added. This is an expensive operation, so we end up saying "List is slower than array".

Of course this is a very simplified explanation, but hopefully enough to paint the picture.

An array is the simplest form of collection, so it's faster than other collections. A List (and many other collections) actually uses an array internally to hold its items.

An array is of course also limited by its simplicity. Most notably you can't change the size of an array. If you want a dynamic collection you would use a List.