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Posted 23 Dec 2010
Licenced CPOL

The ?? Operator

, 4 Sep 2012
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This operator is introduced to set value in place of null value, it can also be defined in words like 'In case of null, pick value from another'


Operator is introduced with Nullable datatype inclusion in .NET Framework operator ?? can also be referred in words like 'In case of null, pick value from another'.


Suppose you're assigning a value to Nullable bool like:

bool? b = null;
At the time of checking value, it will give you an error like:

if(b) //Error CS0266.

So it's always preferable to use ?? to prevent error like:

if(b ?? false)

It defines that, in case b is null, pick the value false.

?? can also be used in multiple choice of value like:

bool ? a = null
bool ? b = null
bool ? c = true
a = b ?? c ?? false;

That will check b first if b is undefined or null, then it will move further to check for c if that also has null then it will set false to a.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


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Hiren solanki
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Comments and Discussions

General@JH64 : Thanks. Yes that's some excessive white space while ... Pin
Hiren solanki27-Dec-10 20:28
memberHiren solanki27-Dec-10 20:28 
GeneralHiren, unfortunately, adding "Also, it is not limited to nul... Pin
Sergey Alexandrovich Kryukov27-Dec-10 20:28
memberSergey Alexandrovich Kryukov27-Dec-10 20:28 
General@brad : I haven't said it's limited to NULL only I said it w... Pin
Hiren solanki27-Dec-10 20:27
memberHiren solanki27-Dec-10 20:27 
GeneralReason for my vote of 4 Nice. I will try to use ??. I think... Pin
JH6427-Dec-10 7:16
memberJH6427-Dec-10 7:16 
GeneralIt is called the null-coalescing (or coalesce) operator. It... Pin 6:35 6:35 
General@SledgeHammer01 : It was just reference from MSDN, Not copy ... Pin
Hiren solanki23-Dec-10 18:33
memberHiren solanki23-Dec-10 18:33 
SuggestionRe: @SledgeHammer01 : It was just reference from MSDN, Not copy ... Pin
Clifford Nelson7-Sep-12 14:29
mvaClifford Nelson7-Sep-12 14:29 
GeneralRe: @SledgeHammer01 : It was just reference from MSDN, Not copy ... Pin
Hiren solanki7-Sep-12 18:50
memberHiren solanki7-Sep-12 18:50 
GeneralReason for my vote of 5 nice tip Pin
Sandesh M Patil23-Dec-10 5:32
memberSandesh M Patil23-Dec-10 5:32 
GeneralReason for my vote of 2 copy and paste from MSDN Pin
SledgeHammer0123-Dec-10 5:11
memberSledgeHammer0123-Dec-10 5:11 

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