Now I have a problem, I wanna add a UltraWebGrid in the row template control the sql will according to different row selected to change.
How can I retrieve the data from the selected row data in "code behind" file(.ascx.vb) for further sql selection?
Unless you want to implement some custom AJAX, you'll need to have your data already available on the client. The simplest way to do this is to have the data you want in columns of your WebGrid, whether you show those columns to the user or not. You'll also want to copy the data back to the corresponding WebGrid cells when you're done editing the template, and use the grid's events to process updates to your underlying data.
If you're using controls that don't take a "value" attribute to store their value (which includes all NetAdvantage for ASP.NET controls), you'll need to use some JavaScript to copy the values into the row edit template's controls and back to the grid. An example of how to do this is provided in the following article from our online Knowledge Base:HOWTO: Placing complex controls into the RowEditTemplate