Question

Can someone explain what’s wrong with the following method signature written using C# 4.0?

public void Test(string arg1 = string.Empty, DateTime arg2 = DateTime.MinValue){}

I understand the difference between “” and string.Empty in terms of compile time checking but surely the way that optional parameters have been implemented in C# 4.0 is pretty inadequate if you can’t declare a reasonable value type null style comparisson?

Answer 1

Because DateTime.MinValue and DateTime.MaxValue aren’t compile time-constants — they’re readonly fields that are initialized at run time by DateTime‘s static constructor.

See the difference between const fields (which are compile-time constants) and readonly fields (which aren’t): What is the difference between const and readonly?