Question:
Possible Duplicate:
What is the “??†operator for?
I have recently come across the ?? operator in C#. What does this operator do and when would someone use it?
Example:
string name = nameVariable ?? string.Empty;
Solution:1
The ?? operator basically means "or if it is null, blah". It is equivalent to:
string name = (nameVariable == null) ? string.Empty : nameVariable; Which, if you're not familiar with the syntax, is basically:
string name; if (nameVariable == null) name = string.Empty; else name = nameVariable;
Solution:2
It's a null-coalescing operator It will right part if the left one is null.
The interesting fact is that you can even use it like this:
string temp = (first ?? second).Text and it will return Text property of the 'second' variable if 'first' is null.
Solution:3
It has the catchy title of the Null Coalescing Operator. What it does is evaluate an expression and then if the expression is null it returns the right-hand operand, otherwise it returns the left-hand operand (ie. the original value).
Using your example as a basis you'd get these results:
string nameVariable = "Diplodocus"; string name = nameVariable ?? string.Empty; // assigns name the value "Diplodocus" And...
string nameVariable = null; string name = nameVariable ?? string.Empty; // assigns name the value String.Empty; Note you can use it with any reference or nullable type, not just strings.
Solution:4
It is equivalent to checking for null and setting the value to something if the first one is. Your statement above is equivalent to:
string name = nameVariable == null ? string.Empty : nameVariable;
Solution:5
It is a null reference check if nameVariable is null it would return an empty string.
Solution:6
The expression
value1 ?? value2 returns value1 if value1 is a value different from null, and returns value2 if value1 equals null.
Note:If u also have question or solution just comment us below or mail us on toontricks1994@gmail.com
EmoticonEmoticon