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

Question

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

When would you use one over the other?

Answer 1

Just to add, readonly for reference types only makes the reference read only not the values. For example:

public class Const_V_Readonly
{
  public const int I_CONST_VALUE = 2;
  public readonly char[] I_RO_VALUE = new Char[]{'a', 'b', 'c'};

  public UpdateReadonly()
  {
     I_RO_VALUE[0] = 'V'; //perfectly legal and will update the value
     I_RO_VALUE = new char[]{'V'}; //will cause compiler error
  }
}