Why GetEnitiesAsync does not behave consistently for me?

I am building a web that uses IB layer to access a database. Most user requests involve reading data from db. So, I created a single instance of PM at the application start up and let each request thread to call the GetEnitiesAsync on this PM. All the code worked. I got the data. And the data displayed on the web pages correctly. But the whole process is erratic. Very often the GetEntitiesCompleted returns no data. And the Error property of GetEntitiesCompletedEventArgs shows this error:

 

"xxxAsync methods can only be called from applications running in a SynchronizationContext that supports thread synchronization. This means, in general, applications running in a WinForms or ASP.NET environment.  Console or WindowsService applications must use BeginInvoke and EndInvoke mechanisms instead"

 

The call is from a WebForm. The application is created with VS 2008. I also verified that SynchronizationContext.Current is not null on the calling thread. So, why is the underneath call behaviour inconsistent?

Aha, I see the problem. The WebForm page that I am using to call the GetEntitiesAsyn is an asynchronous page. According the Microsoft document (http://msdn.microsoft.com/en-us/magazine/cc163725.aspx) this page will be attached to different threads before and after the call to the asynchronous external function. This is the only reason that I can think of why your library sees two different thread ID.  If this is the case, it means GetEnitiesAsyn is not suitable for the asynchronous page then?

GetEntitiesAsync is more a means of making non-blocking data requests than of sharing a PM.  When GetEntitiesAsync returns it always tries to merge its results into the PM cache, and requires that this merge occur on the same thread that made the request (and presumably the same thread that created the PM).  The PM cache does not intrinsically support any type of multi-threaded access - either read or write. 

There is some initialization overhead when constructing a PM, especially the first time when some statics are created, but in order to ensure reliable results it may be your best alternative.   Connect() logic is quite fast if you are not using a BOS, and even if you are using a BOS, Connect() calls after the first are usually fast.  Login() logic may actually be a bit slower, esp. if you've implemented a LoginManager, and a Login is always implicitly done when needed prior to any fetch.

No, there's no set limit on the number of created / connected / logged in PMs.