Does anyone know of a C # library (preferably open source) that can be implemented to calculate the general mood of some given text?
Take a look at the open source mood analysis engine based on Naive Bayes classification at https://github.com/amrishdeep/Dragon .
http://rapid-i.com/content/view/26/84/
maybe not C #, but I think you can call it with C #, will it do the job for you?