: ?? , . .
// ??
Using System;
class NullableDemo2 {
// , static double GetZeroBalO {
Console. WriteLine (" GetZeroBalO."); return 0.0;
}
static void Main() {
double? balance = 123.75; double currentBalance;
// GetZeroBalO , // balance . currentBalance = balance?? GetZeroBalO;
Console.WriteLine(currentBalance);
}
}
GetZeroBal () , balance . , ?? , .
,
, . : <, >, <= >=, , , .. null. .
byte? lower = 16; byte? upper = null;
// lower , upper , if(lower < upper) // %
, , . , , , .
if(lower > upper) //.. !
, , . , (null) .
== ! = , . , .
if(upper == null) //...
bool?, : true (), false () null (). & | bool?.
Q
P 1 Q
P&Q
True
Null
True
Null
False
Null
Null
False
Null
True
True
Null
Null
False
Null
|
|
False
Null
Null
Null
Null
, ! bool?, (null), (null).
2.0, C# , . partial. .
partial , :
partial _ {//...
_ , , . partial.
, , . .
partial class XY {
public XY(int a, int b) {
X = a;
Y = b;
}
}
.
partial class XY {
public int X { get; set; }
}
, .
partial class XY {
public int Y { get; set; }
}