Chapter I: Net architecture (1)

1、C# And .NET The relationship between

  C# The compiler is designed for .NET, This means using C# All the code you write is always .NET Framework Run in . about C# language , Two important conclusions can be drawn ：
（1）C# The structure and methodology of .NET Basic methodology .
（2） in many instances ,C# The specific language functions of depend on .NET The function of , Or depend on .NET Base class .
C# The importance of is reflected in the following two aspects ：

• It is dedicated to Microsoft Of .NET Framework Designed for use with （.NET Framework It is a platform with rich functions , Developable 、 Deploy and execute distributed applications ）.
• It is a language based on modern object-oriented design method , When designing it ,Microsoft It also draws on the experience of all other similar languages .
  C# In itself, it's just a language , Although it is used to generate oriented .NET The code of the environment , But this province is not .NET Part of ..NET Some features supported ,C# Does not support . and C# Other features supported by the language ,.NET But I do not support （ Such as operator overloading ）！

2、 Common language runtime

  .NET Framework The core of is its runtime execution environment , It's called the common language runtime （CLR） or .NET Runtime . Usually will be CLR Code that runs in control is called managed code （managed code）.
   however , stay CLR Execute the written source code （ Use C# Or code written in other languages ） Before , They need to be compiled . stay .NET in , Compilation is divided into two stages ：
（1） Consider the source code as Microsoft Intermediate code （IL）.
（2） hold CLR hold IL That is, the platform specific code .
  Microsoft Interlanguage and Java Keywords share an idea ： They are all low-level languages , The grammar is very simple （ Use numeric codes , Not text code ）, It can be converted to local machine code very quickly . For code , This well-designed general syntax has important advantages ： Platform independence 、 Improve performance and language interoperability .

2.1、 Platform independence

   First , This means that the same file containing bytecode instructions can be placed on any platform . The final stage of the run-time compilation process can be easily completed , In this way, di'ama can run on a specific platform . In other words , I thought that the intermediate language could be obtained .NET Platform independence , This is the same as thinking Java Bytecode will get Java Platform independence is the same .

2.2、 Improve performance

   actually ,IL Than Java Bytecode is even more important .IL Always compiled on the fly （ be called JIT compile ）, and Java Bytecode is often interpretative .Java One of the disadvantages of , When running the application , hold Java The process of converting bytecode to internal executable code will lead to the loss of myocardial infarction .
  JIT The compiler does not compile the entire application at once （ This will have a long start-up time ）, Instead, compile only the part of the code it calls （ This is the origin of its name ）. Once the code has been compiled , The resulting local executable is stored , Until you exit the application , So the next time you run this part of the code , There is no need to recompile .
   trusteeship IL Code executes almost as fast as native machine code , The reason is that the last part of the compilation process is done at run time ,JIT The compiler knows exactly what type of processor the program is running on , Any features or specific machine code instructions provided by the processor can be used to optimize the final executable code .
   Traditional compilers optimize code , But their optimization process is independent of the specific processor running the code . This is because the traditional compiler compiles the executable code of the local machine before releasing the software . That is, the compiler does not know the type of processor running the code ,

1.2.3、 Language interoperability

   Use IL Not only does it support platform independence , It also supports language interoperability . In short , Is to be able to compile any language into an intermediate language , Code compiled into an intermediate language can interoperate with code compiled from other languages .
（1）VB
（2）VC++
C++ An interesting problem with is when compiling into managed code , The compiler can generate a program that contains embedded local executables IL. This means that in C++ You can combine gate types and unmanaged types in your code , So trusteeship C++ Code ：

class MyClass

Defines a common C++ class , The code ：

ref class MyClass

Generated a managed class , It's like using C# or VB2012 Just like writing classes . actually , trusteeship C++ Code ratio C# The better thing about the code is that it can be hosted C++ Calling unmanaged... In code C++ class , Instead of this Yong COM Interoperability features .
   If you use... On managed types .NET Unsupported feature （ for example , Multiple inheritance of templates or classes ）, The compiler will get an error . in addition , When using the exit class , You also need to use non-standard C++ function .
   Written using .NET Of C++ The program will get several different interoperability scenarios . Use compiler settings /clr When common language runtime support is enabled , You can completely mix all local and managed C++ function . Other options can limit C++ Use of the pointer , So as to use C# and VB Write safe code like that .
（3）COM and COM+
Technically speaking ,COM and COM+ Not for .NET Technology , Because components based on them cannot assume that IL（ But if the original COM Components are made of C++ Compiling , Then use hosting C++ To some extent, this can be done ）. however ,COM+ Still an important tool , Because it contains some .NET Features not available . in addition ,COM Components can still be used –.NET Inherited COM Interoperability of , This allows managed code to call COM Components ,COM Components can also call managed code . In general , Write the new build as .NET Components , Mostly for convenience , Because it can make use of .NET Other benefits of base classes and managed code .
（4）Windows Runtime