Type result with Ternary operator in C#
- by Vaccano
I am trying to use the ternary operator, but I am getting hung up on the type it thinks the result should be.
Below is an example that I have contrived to show the issue I am having:
class Program
{
public static void OutputDateTime(DateTime? datetime)
{
Console.WriteLine(datetime);
}
public static bool IsDateTimeHappy(DateTime datetime)
{
if (DateTime.Compare(datetime, DateTime.Parse("1/1")) == 0)
return true;
return false;
}
static void Main(string[] args)
{
DateTime myDateTime = DateTime.Now;
OutputDateTime(IsDateTimeHappy(myDateTime) ? null : myDateTime);
Console.ReadLine(); ^
} |
} |
// This line has the compile issue ---------------+
On the line indicated above, I get the following compile error:
Type of conditional expression cannot be determined because there is no implicit conversion between '< null ' and 'System.DateTime'
I am confused because the parameter is a nullable type (DateTime?). Why does it need to convert at all? If it is null then use that, if it is a date time then use that.
I was under the impression that:
condition ? first_expression : second_expression;
was the same as:
if (condition)
first_expression;
else
second_expression;
Clearly this is not the case. What is the reasoning behind this?
(NOTE: I know that if I make "myDateTime" a nullable DateTime then it will work. But why does it need it?
As I stated earlier this is a contrived example. In my real example "myDateTime" is a data mapped value that cannot be made nullable.)
