Nullable DateTime是否正常工作？

Question

Please check following code

DateTime? tmp = new DateTime();
tmp = null;
return tmp.ToString();

It returns String.Empty .

Is it correct?

May be it will be better to rise exception in second line of code

Answer 1

Yes, it's correct. From the documentation

The text representation of the value of the current Nullable<T> object if the HasValue property is true, or an empty string ( "" ) if the HasValue property is false.

Note also that Nullable<T>.Equals and Nullable<T>.GetHashCode do not throw in this case but that Nullable<T>.GetType does throw. This is because Object.Equals , Object.GetHashCode and Object.ToString are overridden for Nullable<T> but that Object.GetType is not (because it can not be as it is not marked as virtual ).