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

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

Input string was not in the correct format

“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:

1.  Wrap my Date? object instance in a CType, converting to type Date.

2.  Call ToString() on the converted value:

Sanity… recovered.

  • MarkAzali

    thanks for this.


    I wonder why you’re using vb.NET. :)