This forum is for yEd questions only. For questions regarding one of the yFiles programming libraries, please contact yWorks support by mail. (Please include your yWorks customer or evaluator ID in your mail when doing so.)
Your question started with "I am considering building a Windows Forms application [...]". How is this in any way related to yEd? yEd is a finished application you may use to create diagrams. Moreover, yEd is not a Windows Forms application but a Java application.
On the other hand, you may use the yFiles programming libraries for building Windows Forms application.