// .
Using System;
class NullableDemo { static void Main() { int? count = null;
If (count.HasValue)
Console.WriteLine(" count : " + count.Value);
Else
Console.WriteLine(" count ");
count = 100; if(count.HasValue)
Console.WriteLine(" count : " + count. Va^lue);
Else
Console.WriteLine(" count ");
}
}
.
count count : 100
, . , . . , .
.
// .
Using System;
class NullableDemo { static void Main() {
int? count = null; int? result = null;
int incr = 10; // incr
// result ,
// count , result = count + incr; if(result.HasValue)
Console.WriteLine(" result : " + result.Value);
Else
Console.WriteLine(" result ");
// count ,
// result .
count = 100;
result = count + incr;
If(result.HasValue)
Console.WriteLine(" result : " + result.Value);
Else
Console.WriteLine(" result ");
}
}
.
result result : 110
??
System. InvalidOperationException, . , , , . , ??, . , , . .
|
|
|
??.
_?? __
_ , ?? . ?? __.
, balance . currentBalance 0. 0, , .
double? balance = null; double currentBalance;
currentBalance = balance?? 0.0;
balance 123.75.
double? balance = 123.75; double currentBalance;
currentBalance = balance?? 0.0;
