Difference between const and readonly in C#

Question

Hi What is the difference between const and readonly in C#.Net?

Santhosh Kumar Jayaraman · Answer

' const ': Can't be static. Value is evaluated at compile time. Initiailized at declaration only. ' readonly ': Can be either instance-level or static. Value is evaluated at run time. Can be initialized in declaration or by code in the constructor.

Vulpes · Answer

The 'const' modifier is applied to a field or local variable whose value can never change. It is evaluated at compile time and can only be one of the built-in types such as int bool char double string etc which support literals. In contrast the 'readonly' modifier can only be applied to a static or instance field - it can't be applied to a local variable. Also it can only be given a value either where it's defined or within the enclosing type's constructor and cannot be changed after that. However it's value is not determined until runtime and can therefore be of any type not just the built-in types.