I have a problem where a rad chart displays one bar only when the underlying data source returns data for multiple bars. Any idea why only the first bar is showing?
This depends on your implementation as well as how the data is being returned. Depending on how you are setting up your RadChart you could be defining it to only display the first bar. Are you assigning your data source to a data set and then setting this to the RadChart's data source? (RadChart1.DataSource = ds; for example)? Have you checked to see if that one bar isn't a summation of all of your data?
Are they all assigned to one series? or are there multiple series? If you try accessing RadChart1.Series[x] where x is 0 to whatever number of series you have, does it give an error after 0? This would mean that you're either not binding correctly or you have one series.
You could also test manually setting RadChart1.Series[x].Visible = true; For all of your series just to ensure that there is no setting that is preventing them from being displayed.