C# Collections Fundamentals

Question 1

What are Collections?

Answer 1

• collections manage groups of objects in memory
• collections are generic
• objects in collections referred to as Elements

Question 2

What are 3 types of Collections?

Answer 2

• Lists - good for memory use, efficient at accessing elements, usually zero based indexed
• Dictionaries - access elements using a key, most are implemented under covers using a hash table, generally list w/ index have perf edge of dict with key
• Sets - collections designed to combine to form new collections… unions, intersections, etc, not meant to lookup individual elements

Question 3

What is an Array?

Answer 3

• arrays have always been strongly typed in .NET 1.0
• index based lists
• rich API, special synctax, very lightweight

Question 4

Why are Array sizes fixed?

Answer 4

• when initialized Arrays hold a certain block of memory
• accessing items by index just counts bytes and positions in that memory block
• to expand array, no guarantee that neighboring block of memory would be available

Question 5

Arrays - for loop vs foreach loop?

Answer 5

• for an array the for and foreach are essentially same
• foreach does for loop under the covers
• for arrays, item in foreach is readonly