not null date field

not null date field

Is there a way to create a "not null" condition to indicate that an email has to be send when the date field is not empty?

Something that replaces null on the code below

  1. if (input.Date_Time1  !=  null)

I have also tried

  1. if (input.Date_Time1  !=  null)
    {
      //do nothing
    } 
    else
    {
      //send email
    }
but it is not working.