Hello Everybody, I have generate the problem while open File in MAC. it works successfully in windows. System.Diagnostics.Process.Start("C:\\help.pdf" ); -- View this message in context: http://mono.1490590.n4.nabble.com/how-to-open-file-tp3081832p3081832.html Sent from the Mono - WinForms mailing list archive at Nabble.com.