Kimj,

So, one way is to not sharing the PM and make synchronous calls to it. I implemented that as my first attempt. But when I saw the nature of my request processes had a large number and short life, I started to worry about the efficiency of creating new PMs every time. I am not sure how heavy the PM object is, and how intensive it is to connect and disconnect. With your internal knowledge, would you recommend using it that way?

Another way is to create a wrapper around the PM, let’s call it MyPM. MyPM should have a delegate called MyGet. MyGet can be called asynchronously from the asynchronous pages. But what I do inside this function? Call your GetEnities synchronously? I will need to implement locking to prevent the concurrency. This would be a bottleneck. Call you GetEntitiesAsync? I still need to block myself to wait for the result, which is also bottleneck.

Maybe I also need to implement MyGet as a asynchronous call and implement a MyGetComplete event. I implemented this idea once. I also got the same exception I stated earlier. Maybe I didn’t implement it completely right. Within DevForce or your customers, has anybody else encountered the same issue?

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. 

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?