Wikipedia
NCryptoki
NCryptoki is a library for .NET framework that implements the PKCS#11 specifications and supplies an API for C#, VB.NET, Visual Basic 6, Delphi and other COM interop languages for integrating a PKCS#11 compliant token in any application. NCryptoki maps the cryptoki's functions defined in PKCS#11 specifications in a set of high level .NET classes for C# and VB.NET and proposes a programming paradigm that allows to integrate your PKCS#11 compliant token in your applications with a few lines of code. NCryptoki supplies also a Silverlight 5 assembly and a COM interface that allows to use the supplied classes in any language that supports COM interop like Visual Basic 6, Delphi, etc.