>1. Sorting table by double clicking in column header will not underline this header.

Firstly, the column reacts to a click- a double-click is not necessary.

>Sorting is invisible. Is it possible to add underlining or some other visual property to output so that user can see by which column table is sorted?

Sure. You can study the output of the class (specifically, the XSL section) to see how the XSL builds the HTML output using the XML. All it would take is a simple conditional in the first loop (that builds the table header) to alter for the header that was just clicked.

>2. For long table, sorting takes some time.

Curious, how many records are you dealing with? I don't think there's really anything you can do about performance- there's no native way to 'index' XML on the client.

>Is it possible to change mouse cursor to hourglass when sorting is in progress ?

Not sure how to help there either...


>3. Where to find more examples about sorting xml data in client side and for document entry: adding many rows having one document header.

You might check out http://www.vbxml.com- they have some pretty good examples of client side XML manipulation.