Set-like collection in C#/.NET

[emirc]

Is there a collection among .NET collection that doesn't allow duplicates?
ArrayList is very suitable for what I need, except it allows duplicate values.
I've searched the System.Collections namespace but couldn't find anything alike.

[Norfy]

Couldn't find one myself so knocked up a simple implementation of Set

[emirc]

Thank you Norfy, very nice implementation.
I was going to implement a set anyway,
just wanted to check if there's already an implementation among .NET's collections.

[Norfy]

No problem, just thought I would save you some typing.

For that alone could you 'rate this post'?

[emirc]

I would like to, but...

You must spread some Reputation around before giving it to Norfy again.

[Norfy]

Ah yes, multiple inheritance post

[emirc]

Ah yes, multiple inheritance post

Yes.

[Norfy]

I learnt this from you,didn't get why you used a hashtable while you set every key to null..wel we could also use an IList..

Quite simply, the behaviour of the keys collection of a Hashtable is that of a set.
For small sets then an IList is ok but for larger sets a Hashtable is quicker.

[emirc]

there are some interesting collections that NHibernate uses...
the DLL is Iesi.Collections.
I don't know the licensing policy, but i think they're ok generally.

[mehdi62b]

For small sets then an IList is ok but for larger sets a Hashtable is quicker.

we want to just look for in an collection and keys in hashtable are just an ICollection ...hastable is fast but when we give a key and want its item,well its time is O(1)
but when we want to get whether an item is included or not..
no difference between a hashtable(keys) and IList...(both of them are an ICollection)
both of them have O(n).

[Norfy]

Sorry mehdi62b I couldn't follow your comment.

Whether you ask a Hashtable for a value or if it contains a key the access time is not linear O(n) , it uses hashing for both.

The keys are returned as an ICollection but are not implemented as such internally.

[mehdi62b]

Whether you ask a Hashtable for a value or if it contains a key the access time is not linear O(n) , it uses hashing for both.

I meant when we ask a hashtable whetere it contains a key the time is not O(1)..I meant it doesn't use hashing...
and you tell it use hashing(how?) ..I don't know exactly..
no problem...should have a look at one of my book

[Norfy]

I meant it doesn't use hashing...and you tell it use hashing(how?) ..I don't know exactly.

Have you checked out Reflector yet?

Nice tool, lets you browse the (decompiled) core .NET libraries.

[mehdi62b]

I will check that link

[mehdi62b]

Hi Norfy,
thank you very much for that link..I didn't know it..its very usefull tool
and yes,you were right..

public virtual bool Contains(object item);Declaring Type:System.Collections.ArrayList

public virtual bool Contains(object item)
{
	 if (item == null)
	 {
			for (int num1 = 0; num1 < this._size; num1++)
			{
				 if (this._items[num1] == null)
				 {
						return true;
				 }
			}
			return false;
	 }
	 for (int num2 = 0; num2 < this._size; num2++)
	 {
			if (item.Equals(this._items[num2]))
			{
				 return true;
			}
	 }
	 return false;
}

and it clearly shows it has O(n)

and to be countinued...