Which one is better from arraylist and list<object> in C#

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Can someone please help me to clear this topic that which one is better to use between arrayList and List<object>

What I have tried:

No doubt List<> is better but what about in this case i.e list of objects

Posted 15-Nov-18 20:15pm

Member 14056515

Updated 18-Nov-18 21:16pm

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OriginalGriff · Answer 1 · 2018-11-15T20:31:00

Solution 2

List<T> is better because it's strongly typed - which means it only contains objects you expect, and you don't have to cast them when you use them.

If you create a List<object> then you throw away that strong typing and you are back to effectively using an ArrayList again, albeit with a more modern appearance.
I.e. it's a stupid thing to do - always create a List<T> with a fully defined type.

Posted 15-Nov-18 20:31pm

OriginalGriff

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Member 14056515 16-Nov-18 3:23am

basically i want to create a list of objects,for that purpose i'm confused what would be the best way to do performance wise.
please if you could help me with any code snippet

OriginalGriff 16-Nov-18 3:38am

Basically don't create a List of objects - what purpose would you have for them that wouldn't be better served by a strongly typed collection?

Remember that we can't see your screen, access your HDD, or read your mind - we only get exactly what you type to work with. So unless you type what you mean we don't get any context to help us understand your problem!

Aydin Homay 16-Nov-18 6:58am

But even having List of objects is better than using ArrayList because of low overhead of List<T>

OriginalGriff 16-Nov-18 7:13am

Erm ... no. Have a look at the reference sources, and you'll see they are pretty much the same code.
https://referencesource.microsoft.com/#mscorlib/system/collections/arraylist.cs,3e3f6715773d6643
https://referencesource.microsoft.com/#mscorlib/system/collections/generic/list.cs,cf7f4095e4de7646

Aydin Homay 16-Nov-18 7:14am

Exactly after having a look, I wrote that. ;-)
I think go little bit more deep with those codes

MadMyche 16-Nov-18 7:52am

Most likely not. Any overhead that you see is going to be dependent upon what you are trying to do with it. As you have not shared the context of the question it is hard to show you what is best. Remember that ArrayList, List, etc are all collections of objects.

Aydin Homay 16-Nov-18 8:00am

List<t> has more strict and less stressed Add than ArrayList, then List<t> provides an extra interface (IReadOnlyList<t>) which ArrayList does not. Add in ArrayList returns int while in List<t> does not return anything this by itself is performance improvement because returning value from function has Stack overhead.

lmoelleb · Answer 2 · 2018-11-15T20:38:00

Solution 3

For objects it technically does not matter.

ArrayList (and the other non-generic lists) are left in .NET to keep it backwards compatible. They would not have been there if .NET had supported generics from the start.

So just forget ArrayList exist, so your list of objects use the same types as everything else. It keeps the code a bit more consistent.

Posted 15-Nov-18 20:38pm

lmoelleb

Updated 18-Nov-18 21:10pm

v2

Comments

Member 14056515 16-Nov-18 5:14am

Hey,
No doubt List is better than ArrayList performance wise but i'm particularly stuck at the point that List<object> and ArrayList<> will be same because arraylist also takes object as value
so what i am confused about is Which one is better while working with objects

OriginalGriff 16-Nov-18 7:20am

Why do you think there is a performance difference - see my reply to Aydin, and look at the reference sources; you'll see that the code is pretty much identical for the two!

Aydin Homay 16-Nov-18 8:01am

I do not agree with OriginalGriff I also mentioned on my answer but I will say again:
List<t> has more strict and less stressed Add than ArrayList, then List<t> provides an extra interface (IReadOnlyList<t>) which ArrayList does not. Add in ArrayList returns int while in List<t> does not return anything this by itself is performance improvement because returning value from function has Stack overhead.

OriginalGriff 16-Nov-18 8:16am

It's not that simple.
The IL that is generated from the C# code is stack based, so there is a very good chance that the IL performance for returning the value and not returning it will be the same anyway. And the native code that the IL is translated into will likely be register based so it's very possible that the return value will be held, manipulated and returned in a register in the "real world" negating any advantage!

The only way to tell if there is a significant performance difference is to write the same code using the two constructs and performing the same operations several million times and timing it.

The ArrayList will probably be a lot slower in the real world because of the extra validation overhead in casting the objects back to a usable type - but I'd not necessarily put money on it! :laugh:

Aydin Homay 16-Nov-18 8:23am

First, we can not talk based on chance or likelihood. I have not seen their IL and I don`t know so as an engineer I prefer to see the worth case scenario. Second I have studied about the performance of List vs Array and some other collections as well (not ArrayList because it is a legacy collection and most probably is going to be dropped form some point of time from the .Net or at least it was clear for me that will be slow because of implementation complexity that it has) the result of my study is documented at the following link:
https://www.codeproject.com/Articles/1258660/Large-Collections-in-Csharp-Managed-Code-Part-II
I have run several million with several iterations and collected average execution times.

Aydin Homay · Answer 3 · 2018-11-15T20:30:00

Hi,

The answer to your question is a bit difficult because it depends on the type of object, length of collection and operations that need to be done on the collection and even those operation`s frequency. But, to get a good landscape about the performance of collections in .Net I will redirect you to my article that shows you results of a benchmarking in this scope.

Large Collections in C# (Managed Code) - Part II[^]

About only ArrayList vs List I should mention that ArrayList belongs to the time that.Net didn`t have generic List<t>. In fact, the List<t> supports storing values of a specific type without casting to or from the object (No boxing/unboxing overhead). ArrayList simply stores object references.

But, even if you don`t use the benefit of generic list and you create a list with a concrete object type still List<t> is better than ArrayList because of several reasons such as:
1- Low overhead in Add method. The ArrayList has more expensive Add method due to checking Contract.Ensures()
2- The List<T> implements the IReadOnlyList<T> while the ArrayList does not. This intefece is very useful when you would like to construct a readonly collection.
3- I would recommand you see the implementation of each of which. ArrayList vs List<t>

If this did not solve your problem then please leave a comment and I will assist you by improving my solution until your problem gets solved.

Cheers,
AH

Sk Imad · Answer 4 · 2018-11-18T21:17:00

Solution 5

A list is better than array list. List is an interface. It extends directly collection.

Posted 18-Nov-18 21:17pm

Sk Imad

Member 14056515 · Answer 5 · 2018-11-16T00:57:00

Solution 4

Thanks a lot
Really appreciate that

Posted 16-Nov-18 0:57am

Member 14056515

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Richard Deeming 16-Nov-18 9:27am

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Which one is better from arraylist and list<object> in C#

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