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What is the “??” operator for?
Debugging some code and found ?? inside the code. What does this mean?
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Most likely the '?' is the ternary operator. Its grammar is: RESULT = (COND) ? ( STATEMEN IF TRUE) : (STATEMENT IF FALSE) It is a nice shorthand for the typical if-else statement: if (COND) { RESULT = (STATEMENT IF TRUE); } else { RESULT = (STATEMENT IF FALSE);
The nullish coalescing operator ( ?? ) is a logical operator that returns its right-hand side operand when its left-hand side operand is null or undefined , and otherwise returns its left-hand side operand.
?? and ??= operators (C# reference)returns the value of its left-hand operand if it isn't null ; otherwise, it evaluates the right-hand operand and returns its result. The ??
The question mark operator, ?:, is also found in C++. Some people call it the ternary operator because it is the only operator in C++ (and Java) that takes three operands. If you are not familiar with it, it's works like an if-else, but combines operators.
?? is the null-coalescing operator for nullable types.
object obj = canBeNull ?? alternative;
// equivalent to:
object obj = canBeNull != null ? canBeNull : alternative;
http://msdn.microsoft.com/en-us/library/ms173224.aspx refer to this for description. it's an operator
The ?? operator defines the default value to be returned when a nullable type is assigned to a non-nullable type.
// ?? operator example.
int x = null;
// y = x, unless x is null, in which case y = -1.
int y = x ?? -1;
// Assign i to return value of method, unless
// return value is null, in which case assign
// default value of int to i.
int i = GetNullableInt() ?? default(int);
string s = GetStringValue();
// ?? also works with reference types.
// Display contents of s, unless s is null,
// in which case display "Unspecified".
Console.WriteLine(s ?? "Unspecified");
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