Error in paper size in print document c#

[Leila67]

//Paper Size
PrintDocument.DefaultPageSettings.PaperSize = new System.Drawing.Printing.PaperSize("PaperA6", 300, 420);

this is the code
But unfortunately nothing happens when I run it
I wanted to print in Paper A6 and use it as a default in simplest way ...
May be I'm wrong ...whats the right code????