Question

to be more specific, I have DateTime? BirthDate

my question is what will happen in this case:

lblBirthDate.Text = myObject.BirthDate.GetValueOrDefault().ToString();

if BirthDate will be null. I have resharper installed, and it doesn’t warn me that I could have a null problem there…

Answer 1

If BirthDate is null, you get the localized string representation of the default instance of DateTime. That is, you’ll get the string representation of 00:00:00.0000000, January 1, 0001.

You don’t get a warning from ReSharper because you don’t have a null problem there. It is not a runtime exception to call Nullable<T>.GetValueOrDefault on a null instance of a Nullable<T>. Instead, you get the default value if you have a null instance. That’s exactly what GetValueOrDefault means: get Value if HasValue is true, otherwise get the default value for the underlying struct type.