Csharp
C# (pronounced as see sharp) is a multi-paradigm programming language encompassing strong typing, imperative, declarative, functional, generic, object-oriented (class-based), and component-oriented programming disciplines. It was developed by Microsoft within its .NET initiative and is one of the programming languages designed for the Common Language Infrastructure.
Site: https://msdn.microsoft.com/en-us/library/z1zx9t92.aspx
Books
OOP in C# Succinctly
Object-Oriented Programming in C# Succinctly provides an introduction to OOP for C# developers. Author Sander Rossel provides overviews and numerous samples to guide readers towards OOP mastery.
C# Code Contracts Succinctly
In C# Code Contracts Succinctly, author Dirk Strauss demonstrates how to use Code Contracts to validate logical correctness in code, how they can be integrated with abstract classes and interfaces, and even how they can be used to make writing documentation less painful.
C# Succinctly
C# is a general purpose, object-oriented, component-based programming language. As a general purpose language, there are a number of ways to apply C# to accomplish many different tasks. With C# Succinctly by Joe Mayo, you will quickly learn the syntax you need to build your own C# applications.
Threading in C#
An extensive article on multithreading in C#. This tackles difficult issues such as thread safety, when to use Abort, Wait Handles vs Wait and Pulse, the implications of Apartment Threading in Windows Forms, using Thread Pooling, Synchronization Contexts, Memory Barriers and non-blocking synchronization constructs.