According to the documentation seen here:

https://docs.microsoft.com/en-us/dot...format-strings

a string format of "D2" looks like it should be a decimal with two digits to the right of the decimal place...or something, anyways. However, "D2" results in an invalid format specifier exception, these days.

I'm pretty sure it WAS working, but I've now had two programs fail because of this. Can anybody say when or why this changed?