C#代码的编译与执行过程（摘自ms inside c#）

1.You write source code in C#.

2.You then compile it using the C# compiler (csc.exe) into an EXE.

3.The C# compiler outputs the MSIL code and a manifest into a read-only part of the EXE that has a standard PE (Win32-portable executable) header.
  So far, so good. However, here@#s the important part: when the compiler creates the output, it also imports a function named _ CorExeMain from the .NET runtime.

4.When the application is executed, the operating system loads the PE, as well as any dependent dynamic-link libraries (DLLs), such as the one that exports the _ CorExeMain function (mscoree.dll), just as it does with any valid PE.
5.The operating system loader then jumps to the entry point inside the PE, which is put there by the C# compiler. Once again, this is exactly how any other PE is executed in Windows.
However, since the operating system obviously can@#t execute the MSIL code, the entry point is just a small stub that jumps to the _ CorExeMain function in mscoree.dll.

6.The _ CorExeMain function starts the execution of the MSIL code that was placed in the PE.

7.Since MSIL code cannot be executed directly—because it@#s not in a machine-executable format—the CLR compiles the MSIL by using a just-in-time (JIT) compiler (or JITter) into native CPU instructions as it processes the MSIL. JIT compiling oclearcase/" target="_blank" >ccurs only as methods in the program are called. The compiled executable code is cached on the machine and is recompiled only if there@#s some change to the source code.

原文转自：http://www.ltesting.net