Date, Date?, and the ToString Method in VB.Net

Fri, 03 Oct 2014 17:28:05 +0000

I just spent the last 45 minutes frustrated as to why I was getting the following exception

“Input string was not in a correct format.” and “[InvalidCastException: Conversion from string “MMMM dd, yyyy” to type ‘Integer’ is not valid.]

I kept thinking to myself, “How hard can this possibly be?!! I’ve done this a thousand times — Why is it wanting to convert my format string into an Integer??! AAHHH!!”. Consulting MSDN on the matter only confirmed that I knew what I was doing with the string formatter.

What got me in the end is that it turns out I didn’t know what I was doing with my Date object. In fact, I wasn’t dealing with a Date object at all. I was dealing with a Date? object (that is, a Nullable(of Date). Date and Date? are not the same. And it matters, because the ToString() method of Date has _different overloads _than the ToString() method of Date?. Only the Date type allows you to put in a format string to fancy up how the date is displayed when it’s converted to a string.

My solution:

Wrap my Date? object instance in a CType, converting to type Date.
Call ToString() on the converted value:

CType(someObject.dateInstance, Date).ToString("MMMM dd, yyyy")

Sanity… recovered.

Nullable Date on Andrew Bancroft

Date, Date?, and the ToString Method in VB.Net

My solution: