Hi and welcome to LQ!
First an advice: choose a title relevant to your question when submitting a new thread. Two good reasons to get into this habit: 1) Your question will have more exposure, since many LQ members tend to ignore threads marked as "Help me", "Question", "Urgent" and so on. 2) Your question and the related answers may serve as a knowledege base to users having the same doubt/question in their mind. If the title is relevant, the LQ search engine can easily find it and your question will help others in the spirit of the Linux community.
Regarding your question, you will find a lot of useful information in the Wikipedia page
. Take a look especially at the last paragraph of the "Standardization - Criticism" section and at the "Implementations" section. I cannot tell for sure, but I doubt you will find any RPM of C# for Red Hat. The project sites of the free implementations may provide more information about this topic.