InfoPath Dev

I add the below formula as a calculated field in the bottom right corner on all views. This helps with support and troubleshooting. I hope you find it useful too.

substring-before( substring-after( /processing-instruction()[local-name(.) = "mso-infoPathSolution"], 'solutionVersion="'), '"')

 Nice, thanks!

I put a text box with this formula,but it stays empty in preview and when it is installed in Central Admin. What can be the reason?

Try making sure that the "Edit XPath" check box in the lower right corner of the formula editor window is checked. Sometimes when pasting a formula to InfoPath, we must first check this box to enable advanced XPath formula editing.