Wednesday, April 27, 2011

Constant_ReadOnly_Static keyword

Constants

  • Constants are static by default
  • They must have a value at compilation-time (you can have e.g. 3.14 * 2, but cannot call methods)
  • Could be declared within functions
  • Are copied into every assembly that uses them (every assembly gets a local copy of values)
  • Can be used in attributes

Readonly instance fields

  • Must have set value by the time constructor exits
  • Are evaluated when instance is created

Static readonly fields

  • Are evaluated when code execution hits class reference (when new instance is created or a static method is executed)
  • Must have an evaluated value by the time the static constructor is done
  • It's not recommended to put ThreadStaticAttribute on these (static constructors will be executed in one thread only and will set the value for its thread; all other threads will have this value uninitialized)

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