Hi,
Here's my approach how will I do it. First bind the xml data source control with gridview then, filter out the distinct values for the columns for which you need dropdown[lets say for country you will filter out all distinct countries available in xml, then populate those values in dropdown]. And then on selection of any dropdown values, you can query the xmlDataSource to give the filtered data.
Could you please provide more information on current state,what to be remembered?
I can stop the page refresh using ajax call.
Message me, we can discuss further.
Thanks.