Details about constant value in C#( from CLR via C#)

　　Because a constant value never changes, constants are always considered to be part of the defining type. In other words, constants are always considered to be static members, not instance members. Defining a constant causes the creation of metadata.
　　When code refers to a constant symbol, compilers look up the symbol in the metadata of the assembly that defines the constant, extract the constant’s value, and embed the value in the emitted Intermediate Language (IL) code. Because a constant’s value is embedded directly in code, constants don’t require any memory to be allocated for them at runtime. In addition, you can’t get the address of a constant and you can’t pass a constant by reference. These constraints also mean that constants don’t have a good cross-assembly versioning story, so you should use them only when you know that the value of a symbol will never change.