CODEWITHSUNDEEP
c#
urz shah
urz shah

Reputation: 481

ArrayList vs Generic List On Memory allocation in C#?

I want to clear concepts regarding Memory allocation of ArrayList vs Generic List, if both are value type and if both are reference type. Could any one hhelp to clear out?

Upvotes: 1

Views: 2491

Answers (3)

Roland Mai
Roland Mai

Reputation: 31077

They are both reference types. The only difference is that ArrayList is weakly typed. Value types such as int, bool etc that are stored in it are boxed into the object type. Then, you unbox them when you cast each item in the ArrayList.

Because everything is boxed into an object, you can store objects of different types in an ArrayList.

Generic List is strongly typed, that is, it can store objects of the same type. There's no boxing, so it's more efficient.

The boxing process allocates more memory to encapsulate the object into the weak type object.

If you stored only objects of reference types in the ArrayList, then boxing is not used, rather another mechanism is used called reference conversion.

Upvotes: 1

Henk Holterman
Henk Holterman

Reputation: 273244

The only difference in memory use is when you store a Value type. The ArrayList will have to Box (copy) the value. A boxed value will be placed on the Heap, consuming at least an extra header block (ca 20 bytes).

But this will only be significant when you store many millions of items, not something you do all the time.

Upvotes: 2

Prabhu Murthy
Prabhu Murthy

Reputation: 9261

  • ArrayList is a Reference Type,but not Typesafe and less efficient
  • List<T> or Generic list is a Reference Type,but is Type Safe and efficient

Here is the SO post on Memory Allocation of Reference Types How memory is allocated to reference types in C#?

Upvotes: 0

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