I think ReSharper should not suggest "To const" refactoring for public static readonly fields for public classes.
public static readonly int SomeConstant = 1; // ReSharper suggest "To const"
Using public constants on public classes could lead some problems:
=== Assembly A ===
public class SomeClass
public const int SomeConstant = 1;
=== Assembly B ===
var a = SomeClass.SomeConstant; // compiler uses _value_ of SomeConstant
when we deploy new version of assembly A (with changes: SomeConstant to 2, e.g.) and place it to the folder with assembly B without recompiling assembly B
we will still get value 1 in our SomeMethod
PS: Sorry if it is duplicate.