This great book shows you the process, thinking and code behind the open-source .NET IDE SharpDevelop that went on to branch into MonoDevelop.
It was not in print for very long but Apress bought Wrox when they closed down and made the book freely available on its site for download in PDF format.
Alas, with their most recent web redesign their free e-books section has disappeared so I am temporarily hosting it here after recommending it to somebody interested in writing their own syntax highlighting editor on the MSDN forums.
Download Dissecting a C# Application - Inside SharpDevelop (Adobe PDF) (3.9MB)
[)amien
Im in two minds about the book, I have the dead tree version somewhere and when .net came out intially this book was interesting but something just didnt sit right with me and I quickly lost interest. I could never put my finger on why, but I tend not to reccomend this to people anymore.
I looked at the linked msdn thread and it seems like the OP doesnt really understand how hard it is to do what he _really_ wants (parse to AST with highlighting) that he is talking about RTF boxes and html pages means he wont grok the books lessons on editing behind the scenes data structure.
The think that put my off initially was the Codon's they introduce right at the start which is basically their name for their plug-in architecture. If you skip that stuff you will probably find yourself referring back but some of the information on designers, syntax highlighting, parsers etc. is well worth persevering with.
[)amien