1. C# and.NET

2. .NET Architecture  Compiling and running code that targets.NET  Advantages of Microsoft Intermediate Language (MSIL)  Value and Reference Types  Data Typing  Understanding error handling and attributes  Assemblies,.NET base classes, and namespaces

3. The Relationship of C# to.NET  C# is always used within the.NET Framework, hence: 1.The architecture and methodologies of C# reflect the underlying methodologies of.NET 2.In many cases, specific language features of C# depend on features of.NET or the.NET base classes.  Because of this dependence: Understanding of he architecture and methodology of.NET is required prior to C# programming.

4. C# Programming 1.Specifically designed for.NET 2.Language is based on present day understanding of design methodologies and Object oriented Principles 3.Must understand.NET framework in order to develop applications in C# effectively.

5. The Common Language Runtime  CLR (Common Language Runtime) is central to understanding C#  Commonly CLR is often termed managed code.  Compilation of C# (and many other languages) occurs in two steps: 1.Compilation of source code to so called Intermediate Langue (IL) 2. Compilation of IL to platform-specific code by CLR.

6. Support for Object Orientation and Interfaces .NET implementation has practical limitations  IL (Intermediate Language) uses a single implementation inheritance of classes.  Working with.NET implies compiling to IL  This in turn means usage of object oriented-programming methodologies  Object Oriented Programming is not sufficient to give you interoperability (e.g., C++ and Java are not interoperable in spite of using the same object oriented programing paradigm).

7. Language Interoperability  So what is exactly language interoperability?  Initially through COM  used to interface various modules of different languages  allowing them to communicate with each other, and/or  instantiate each others modules,  In no way did COM  components written in different languages directly communicate with each other, and/or  Instantiate each others modules  => this was done only through COM intermediation.  In addition COM architecture did not permit implementation inheritance => loss of many Object Oriented Programming features  Debugging requires each component to be debugged independently,  It was not possible to step between languages in the debugger,  Language Interoperability means that classes written in one language were able to directly invoke classes written in another language.  This was achieved in.NET with IL!

8. Distinct Value and Reference Types  Strong Distinction between:  Value:  variables directly stores its data,  Typically stored on the “stack,” and  Reference:  variables that store the address at which the corresponding data can be found  Located in are of memory know as “managed heap”

9. Strong Data Typing  IL is based on “Exceptionally Strong Data Typing”.  Gaines afforded by of enforcing this feature outweighs the performance losses:  Language Interoperability  Garbage Collection  Security  Application Domains: Designed to ease the overhead involved when  Running application that need to be isolated from each other, but  Need to communicate with each other.