well, everything you need to create your own charting library is right there in the core class libraries.
But why go to the trouble (unless of course it's a homework assignment you want to trick us into doing for you) of doing that when there are perfectly good components available?
indeed he is.
In some highly specific situations you may want to avoid any reliance on third parties, but usually you want to write as little code yourself as possible.
Why reinvent the wheel? Why go through months or years of development and testing to get to the stage where those third parties (often highly experienced in their field) are already?
If you go that way, why rely on a programming language written by others?
Why rely on an operating system written by others?
You could even question the decision to use hardware created by others made out of raw materials mined by others with tools made by others...