XML and Datasets - LOST, help

Question

Hi,

I'm trying to create a tiny app to help me learn XML and Dataset.  However I'm unable to get this to work and I think I'm going in circles.  All the examples I have looked at have me at a lost.  I would like my app to write to an XML doc.  I can load the dataset from my XML doc (Airlines.xml) however I can't figure out how to get my dataset to write back to my XML doc.  Does anyone have any suggestions?

My XML doc only has two items (airlines and miles) to make it easy for me to understand the process.  And my form has a save button (which the plan was to update the dataset then update the XML doc) and a view button which at this point the view button works.

Thank you