This is very useful for plotting things in .Net:
Main Page – ZedGraphWiki
Are you looking for a way to draw in .Net? Heres yet another charting class library with a high degree of configurability that is also easy to use.
ZedGraph is a set of classes, written in C#, for creating 2D line and bar graphs of arbitrary datasets. The classes provide a high degree of flexibility — almost every aspect of the graph can be user-modified. At the same time, usage of the classes is kept simple by providing default values for all of the graph attributes. The classes include code for choosing appropriate scale ranges and step sizes based on the range of data values being plotted.