Chart markers in C# and such...

C# (Windows Forms) does not come with any charting controls. You can draw lines with arrows etc if that's the only thing you need. My book Graphics Programming with GDI+ covers styles and shapes of lines.

If you are thinking about more shapes and charts, you can draw charting using GDI+ or GDI but they are not very efficient and there is a lot of work. I would recommend use a third party component such as Nevron, DevExpress, SyncFusion, or GoDiagram. These controls are also will cost you less than what you need to do by yourself. It's just matter of time to find out which component provides you what you're looking for.

WPF has better support for drawing and comes with basic charting components.