I was asked recently about 'ESAPI for .NET?' (by XXX, who is an SI customer) and here was my reply
Hi, unfortunately there isn't a simple answer/solution for your question
I would definitely not recommend of using any of the ESAPI libraries, specially the .NET since that is not even in a workable state.
The best security controls out there are actually the Microsoft ones, which when used in secure ways, do provide a lot of security (for example Razor now encodes by default which does a lot to prevent XSS). On the topic of XSS, the Microsoft AntiXSS library is really good, and is now part of .NET 4.5.