Some Key Differences
Classes and structs
Classes and structs are almost the same in C++ – this is not true for C#. In C#, structs are value types (instances stored directly on the stack, or inline within heap-based objects), whereas classes are reference types (instances stored on the heap, accessed indirectly via a reference). Also structs cannot inherit from structs or classes, though they can implement interfaces. Structs cannot have destructors. A C# struct is much more like a C struct than a C++ struct.
Chars and strings in .NET are 16-bit (Unicode/UTF-16), not 8-bit like C++
There is no '#include' statement – use "using" instead. See here.
There is no '#define' statement – use const instead. See here.
Header Files (*.h)
Nope, not used in C#. See here.
Using C++ code with C#
Where existing C++ code must be used with a new application, the existing code can be wrapped using C++/CLI to allow it to interop with C#.