Hi Mikhail,
The CustomPattern works in conjunction with the Pattern property and allows you to specify a custom on / off line pattern as described on the following page:
http://helpdotnetvision.nevron.com/Presentation_Graphics_AppearanceStyles_StrokeStyle_Stroke_Style.html
For example:
bar.BorderStyle.Pattern = LinePattern.Custom;
bar.BorderStyle.CustomPattern = 0x5555;
bar.BorderStyle.Width = new NLength(2, NGraphicsUnit.Point);
bar.BorderStyle.Factor = 2;
Will make the stroke applied on bars dotted (0x5555 translates to the following binary pattern - 101010101010101). Let us know if you have any questions.