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heres a tricky question on IDictionary.Contains method

Posted on 2006-11-07
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Last Modified: 2008-01-09
i am making new Hashtable() objects all the time in my project.
however i am making them like so :

IDictionary id = new Hashtable();

my question is in regards to both the .Contains() method in IDictionary and the.ContainsKey() method in hashtable.
according to msdn on .ContainsKey() method:
>
This method behaves exactly as Contains.
This method is an O(1) operation.
>

which potentially means that it is faster.

what i want to know is if i use the .Contains() method will it use the underlining .ContainsKey method and therefore i will get O(1) operation? and can u prove this either way.
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Question by:joshuadavidlee
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Expert Comment

by:AngryBinary
ID: 17900495
While either a bechmark test or diassembly is the best way to PROVE this, I think the fact that an index lookup is a non-linear operation implies that any method that essentially and exclusively implements an index lookup (as opposed to an "iterate and search") will be an O(1) operation as well, and going the extra step to demonstrate proof of this is a little excessive unless you have a reeeeeeeeeeeally good reason to suspect otherwise :)

--Randall
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Expert Comment

by:ostdp
ID: 17900905
I just looked into the assembly and I can confirm that Contains calls the ContainsKey method.
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Accepted Solution

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ostdp earned 500 total points
ID: 17900913
This is the code that a decompiler produces:

public virtual bool Contains(object key)
{
      return this.ContainsKey(key);
}

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