How to check if a DateTime field is not null or empty? [duplicate]

Answer 1

If you declare a DateTime, then the default value is DateTime.MinValue, and hence you have to check it like this:

DateTime dat = new DateTime();

 if (dat==DateTime.MinValue)
 {
     //unassigned
 }

---

If the DateTime is nullable, well that's a different story:

 DateTime? dat = null;

 if (!dat.HasValue)
 {
     //unassigned
 }

Answer 2

DateTime is not standard nullable type. If you want assign null to DateTime type of variable, you have to use DateTime? type which supports null value.

If you only want test your variable to be set (e.g. variable holds other than default value), you can use keyword "default" like in following code:

if (dateTimeVariable == default(DateTime))
{
    //do work for dateTimeVariable == null situation
}