var discount = (i == 1) ? definition.SecondPetDiscount ?? definition.AdditionalPetDiscount :
(i == 2) ? definition.ThirdPetDiscount ?? definition.AdditionalPetDiscount :
definition.AdditionalPetDiscount;
Could you any one give me an explanation of this code snippet? I know about the ternary operator. But the above is not like that.
The normal ternary operator looks like this:
PaidDate = ( paidDate == null ? DateTime.Now : paidDate);
?: is the ternary operator. ?? is the null-coalescing operator. It is used to return the first expression that is not null.
The snippet you posted is making use of both operators. It is equivalent to the following if/else construct:
if (i == 1)
{
if (definition.SecondPetDiscount != null)
{
discount = definition.SecondPetDiscount;
}
else
{
discount = definition.AdditionalPetDiscount;
}
}
else if (i == 2)
{
if (definition.ThirdPetDiscount != null)
{
discount = definition.ThirdPetDiscount;
}
else
{
discount = definition.AdditionalPetDiscount;
}
}
else
{
discount = definition.AdditionalPetDiscount;
}
In that snippet they are chaining together multiple ternary operations. It is also sometimes useful to chain together multiple null-coalescing operations, e.g. var foo = a ?? b ?? c.
That's the null-coalescing operator in C#. It is a shortcut that returns the left side (if the left side is not null) and otherwise returns the right side
This is a mix.
In this statement, there are two conditional (ternary) operations, as well as the null coalescing operator.
The second "option" of the first ternary operation is an entire ternary operation itself.
I think you're confused with the null coalescing operator, or the ??
definition.ThirdPetDiscount ?? definition.AdditionalPetDiscount
it means that if definition.ThirdPetDiscount is null, than use definition.AdditionalPetDiscount
the ternary operator around that behaves like a regular ternary operator. the null-coalescing operator is just nested inside of it, and you also have 1 ternary operator nested in a second ternary operator
var discount = (i == 1) ? definition.SecondPetDiscount ?? definition.AdditionalPetDiscount :
(i == 2) ? definition.ThirdPetDiscount ?? definition.AdditionalPetDiscount :
definition.AdditionalPetDiscount;
Of course, the (bool) ? code : code pattern translates to an if - else block.
So we get
var discount;
if( i==1 )
{
discount = definition.SecondPetDiscount ?? definition.AdditionalPetDiscount;
}
else if( i==2 )
{
discount = definition.ThirdPetDiscount ?? definition.AdditionalPetDiscount;
}
else
{
discount = definition.AdditionalPetDiscount;
}
object ?? object is the null coalescing ternary operator. What this does is it will take the first non-null object in the coalescing and return it. There can be any number of objects in the list.
So the var discount here is set to definition.AdditionalPetDiscount if the 2nd or 3rd pet discount is null, or if i is not 1 or 2.
If i is 1 then discount will be set to definition.SecondPetDiscount unless that is null, in which case it will be set to definition.AdditionalPetDiscount.
If i is 2 then discount will be set to definition.ThirdPetDiscount unless that is null, in which case it will be set to definition.AdditionalPetDiscount.
If i is neither 1 nor 2 then it will be set to definition.AdditionalPetDiscount.
DateTime? paidDate = null; var date = paidDate ?? DateTime.Now;You can interpret it as "if paidDate is not null, then return its value, otherwise return DateTime.Now. Notice that the first argument needs to be Nullable, in this caseDateTime???has higher precedence than the conditional operator? :.