Hey, Chris,

You need to check for null values first.

DateTime exitDateTime;

if(Convert.IsDBNull(Dr[drvPortfolio["EnterPriceDateTime"])==false)
   exitDateTime = (DateTime)drvPortfolio["EnterPriceDateTime"];
else
   // whatever you want to do if IsDbNull returns a true

There are variations on that syntax, that's the one I've often used

HTH,
Kevin