[c#] Cannot implicitly convert type 'int?' to 'int'.

If you're concerned with the possible null return value, you can also run something like this:

int ordersPerHour;  // can't be int? as it's different from method signature
// ... do stuff ... //
ordersPerHour = (dbcommand.ExecuteScalar() as int?).GetValueOrDefault();

This way you'll deal with the potential unexpected results and can also provide a default value to the expression, by entering .GetValueOrDefault(-1) or something more meaningful to you.