C# is a multi-paradigm programming language encompassing strong typing, imperative, declarative, functional, procedural, generic, object-oriented (class-based), and component-oriented programming disciplines.
C# can be used with the Salesforce to access objects exposed through the SOAP API.
You can use C# to access the API through objects that serve as proxies for their server-side counterparts. Before using the API, you must first generate these objects from your organization’s WSDL file.
Useful Documentation
