Mr.SuicideSheep Mr.SuicideSheep - 1 year ago 174
C# Question

Type of conditional expression cannot be determined because there is no implicit conversion between System.DateTime and null

DateTime tempDate = calculatesomedatetime();
someDateTimeControl.Value = null; //no issue
someDateTimeControl.Value = (tempDate > DateTime.MinValue)? tempDate : null;



Type of conditional expression cannot be determined because there is no implicit conversion between System.DateTime and null


Line 3 throwing me such error which I don't understand as the comparison is
(tempDate > DateTime.MinValue)
and
null
is just value assignment. Why would compiler interpret this as error?

However if I write as below, it has no problem

if(tempDate > DateTime.MinValue)
{
someDateTimeControl.Value = tempDate;
}else
{
someDateTimeControl.Value = null;
}

Answer Source

The issue is with the ternary operation. You're changing the data type from DateTime to a nullable DateTime. Ternary operations require you to return the same data type both before and after the colon. Doing something like this would work:

someDateTimeControl.Value = (tempDate > DateTime.MinValue) ? (DateTime?)tempDate : null;
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