[Newbie] db web service

Question

Im very new to c# and web services etc and Im having some difficulty understanding how they work. I have a projec to do which involves creating a web service that handles connections to sql db performs queries etc on the db. What I dont understand is how you handle continuity between the methods for a webservice. For example I have public methods which construct the connection string opens the connection closes the connection and performs a select on the database. These are all seperate methods though the open and close are called from the select method. The sql connection string is stored in a private variable in the web service. Is it possible to do it like this? If I call the connection string method first to set the private variable and then the open method will the open method see the value I set? Using the debugging in Visual Studio and accessing the methods directly didnt work for me but I dont know if it will work if called from an asp.net page. Like I said Im new to this so I dont fully understand how it works. Id appreciate any help or advice.

spgilmore · Answer

The webservice is implemented as a class. IIS will create an instance of this class whenever necessary to handle client requests. This means that there are going to be multiple instances of the class. IOW it needs to be treated like a thread class and needs to be thread-safe. Anything that needs to persist between calls should either be stored in a database a memory-mapped file etc. or in a static variable (a global). This is ultimately going to be a DLL and that means that global members only exist once. It is a good idea to put a monitor critical section or multi-read-exclusive-write synchronizer around every access to a global so keep them to a minimum for your own sake.