how show seconds without exponent notation

Question

https://code.sololearn.com/cN51bvxoxtyC/?ref=app
the second floating point value

Answer 1

Try using either of these options:
(decimal) diff.TotalSeconds
//or
diff.TotalSeconds.ToString(
"0." + new string('#', 339)
)
NOTE: The 339 indicates the max number of digits.
There are other options as presented in these responses which are worth reviewing:
https://stackoverflow.com/questions/1546113/double-to-string-conversion-without-scientific-notation

Answer 2

David Carroll you rock!