Multithreading in regards to WCF Service and a Web Service

I read the following article indicating the following:
WCF Services can be multi-threaded via Service Behavior class, while web services cannot be multi-threaded.

See article:

My question is how does a Web Service handle multiple request if it isn't multi-threaded?
Does the request invoke new instances of the web service?
Lawrence AverySystem DeveloperAsked:
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I would say the referenced article is incorrect.  As you correctly identified, IIS is certainly "multithreaded" as is a WCF service and there is nothing stopping you from using additional threads in the middle of a call.  I think the article botched the concept of additional concurrency control options that WCF has within a client session via the ConcurrencyMode behavior.

I think this article has the best example:

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Lawrence AverySystem DeveloperAuthor Commented:
Ok so because the Web Service is hosted by IIS, it can handle multiple request, correct? And the WCF Service can create instances upon a request?

So in essence they both can able to handle Multi-Request without adding coding (Except in the WCF Service modifying the ConcurrencyMode behavior to Multiple?

Here is a very good article on WCF Service on handling request:
Even with the WCF service with ConcurrencyMode=Single, it is still threaded in the same sense that an ASMX service is - requests made by separate clients would be executed on their own worker thread.
Lawrence AverySystem DeveloperAuthor Commented:
From reading the article above, it would seem that the data manipulated in the
( ConcurrencyMode=Single- which means one instance of the WCF Service)
WCF  Service is shared by all the clients calling it. In other words multiple threads access the same WCF Service instance.  There must a Lock on the instance when WCF Service is in Single mode.

Do you have an article on how ASMX handles multiple concurrent request? I know ASMX is hosted by the IIS. You are saying it's multi-threaded. In this case do you really mean that the ASMX is instantiated  by every request to it and  that each instance has its own thread?
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