InfoPath Dev

I see that MainDataSource.CreateNavigator().SelectSingleNode() has an overload to pass XPathExpression. I tried to search for an example of XPathExpression, but without much success. Will XPathExpression help me to filter the nodes based on filter criteria I pass? Thanks.

I want to fire the logic on Submit button click instead of having a cascading drop down.

Hello, I have a secondary data connection that receives data from SharePoint list and I bind this to a Drop-down. Data that I have is as below: Country Name Responsible Person United States Person 1 United States Person 2 United ...