title: Make a .Net DLL Thread-safe for Web App Consumption?
body: <p>I've written a class in VB.Net that is consumed in an ASP.NET Web Application running IIS7. I use .NET Framework 4.0. The class performs a REST request to an online and retrieves an XML response containing strongly typed data. </p>
  
  <p>This class also performs caching using an SQL Server database. The class is compiled to a .DLL and referenced by the Web Application. It works excellent and now I need to know how to make the class thread-safe.</p>
  
  <p>I have no experience with making code 'thread-safe'. I don't know where to begin in determining whether or not it is thread-safe. Am assuming, because I didn't pay attention to this during development, that it is NOT thread-safe and that since it the web application will be used by many users at the same time that it must be payed attention to.</p>
  
  <p>Can anyone point me on how to test for thread-safety? Are there any resources online that that will give me some ideas? Are there any rules of thumb that will tip me off as to where my main concerns are?</p>