How to use PrintDialog.Printvisual for hard coded file name

I am using PrintDialog.Printvisual for export file in pdf format.

But I am not able to set default file name for PrintVisual. following is code.


printDlg.PrintVisual(surface,IO.Path.GetFileNameWithoutExtension(functionchartName));

surface is my printing data and IO.Path.GetFileNameWithoutExtension(functionchartName) is file name.