Author: natan

In table below official recommendations for choosing data structure for your needs:

Generic	Non-Generic	Thread safe	Purpose
Dictionary	Hashtable	ConcurrentDictionary	key value pairs, lookup
List	Array	ImmutableList	access items by index
Queue	–	ConcurrentQueue	FIFO queue
Stack	–	ConcurrentStack	LIFO queue
LinkedList	–	–	access items sequentially
ObservableCollection	–	–	notfications after modification
SortedList		ImmutableSortedSet	auto sorted collection
HashSet		ImmutableHashSet	dictionary of just keys (high performance set operations)

Further read:

https://learn.microsoft.com/en-us/dotnet/standard/collections/

• sequential collection of chars
• immutable
• max 2GB or about 1 billion characters
• reference type
• are interned – CLR saves memory by maintaining a table, called the “intern pool”, that contains a single reference to each unique literal string declared or created programmatically in your program.

Further read:

https://learn.microsoft.com/en-us/dotnet/api/system.string?view=net-7.0

https://learn.microsoft.com/en-us/dotnet/api/system.string.intern?view=net-6.0#remarks

ref struct type can not be used as object field.

Further read:

`ref struct` types

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/ref-struct

• added as part of C# 7.2.
• defined with ref struct StructName
• always on the stack
• never part of heap
• cannot be element of an array
• cannot be field type of reference type
• can’t implement interfaces
• can’t be boxed
• can’t be type argument
• can’t be captured by closure of lambda or local function
• can’t be used in async methods
• can’t be used in iterators

Further read:

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/ref-struct

Value types are stored in the heap when they are part of the reference type.