schematic drawing sdk c#

Was wondering if anyone knew and or used a good sdk for drawing schematics for things such as a circuit boards. So something that will connect and draw lines between logical blocks. Main blocks I would need are a switch box an OR box and an AND box. I prefer it to work in C# because its mostly a windows gui based project, however I am willing to do it in C/C++ if there is a good reason t开发者_开发百科oo.

Just wondering if anyone has ran across something like this in the past, before I start trying to reinvent the wheel with my own code.

Thanks in advance!!