The page is loaded correctly at first but during postbacks in many cases it ends up with error saying that some of DropDowns has a SelectedValue which is invalid because it does not exist in the list of items. In this post I have described the same problem and the solution was to specify the TopMostItem. However - all of dropdowns has the TopMostItem set up!

The page works correctly when I remove these 3 dropdowns. I'm really confused by this behavior and cannot find the cause of this error.

I can email You my project (I cannot post it to whole forum) if necessary.

I really don't know what else to say via the forum past taking the sample that you gave me and trying to point you in the right direction here.  This has more to do with how you dsign your application versus being anything related to StrataFrame.

You must take business logic and design into account here which includes the possibility that you do not have records in one BO while they are in the other.  Now, SF will take a no record situation into account automatically as the bindings get removed in this case to prevent an error.  But from what I can tell, and from the sample that you provided for me to look at, I don't see anything that is SF related.  You would have the exact same issue if you were using data adapters and standard .NET data binding.  I don't of any other way to say this or explain this.

To really help you understand the overall issues that you have within your application are more of a consulting and training issue versus any type of issue with StrataFrame.  The forum is not a good tool for this and is why we provide training classes and the occasional consulting (when we have the time).  But past creating some sample that more accuratly depicts your problem, I am at a loss as to what to add to my comments here.  Sorry