I have a webservice that I use as an application tier for my main software project.  I want to be able to call it as a WCF service but still have my legacy non .net 3.5 apps call it as a regular web service.

Kirk Allen Evan's blog has a great article on how to do this here.  I did this, removed my web service reference in my WPF project, added a service reference to the same location and ended up with 2 errors in my code.  Rather than declaring my webservice object as mywebservicens.mywebservice I had to declare it as mywebservicens.mywebservicesoapclient.  I also had to create the object (new) in this fashion.  Once I did this I was up and running, EXCEPT that my webservice uses session variables.  After going around in circles thinking the problem was with the binding type (basichttpbinding) I discovered that the solution was pretty simple.  In the app.config I had to set allowCookies="true".

I also made some changes that were recommended on Juan Wajnerman's blog.  In my case I implemented suggestions 1 and 4 from his blog.  Finally, I had to set the maxBufferSize and maxReceivedMessageSize to a larger number as I am returning datasets that are larger than the default 65,536 byte value.  Once these changes were made my application worked great calling this as a WCF service.  My legacy applications still worked in the legacy manner and for now all is good.  Once I migrate all of my clients to WCF I will finish the job by following this link from msdn to properly move things into interfaces etc. the way a new WCF service would be.

Sean