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Posted 23 Dec 2010

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

GeneralReason for my vote of 5 Good to remind people about (new) la... Pin
johannesnestler21-Feb-12 4:39
memberjohannesnestler21-Feb-12 4:39 
GeneralReason for my vote of 5 nice one Pin
nikhi _singh9-Feb-12 2:45
membernikhi _singh9-Feb-12 2:45 
GeneralReason for my vote of 5 Simple tip; Doesn't matter if I coul... Pin
Justin Helsley6-Oct-11 10:23
memberJustin Helsley6-Oct-11 10:23 
Reason for my vote of 5
Simple tip; Doesn't matter if I could have looked it up on MSDN...
GeneralReason for my vote of 5 Completly forgot about this operator... Pin
sucram16-Jan-11 23:45
membersucram16-Jan-11 23:45 
GeneralAre you gonna now describe other operators as well? :) Pin
jszczur3-Jan-11 12:57
memberjszczur3-Jan-11 12:57 
GeneralThank you bob. Pin
Hiren Solanki28-Dec-10 19:14
memberHiren Solanki28-Dec-10 19:14 
GeneralReason for my vote of 5 Very usefull in database data Pin
Bob Baeck28-Dec-10 10:09
memberBob Baeck28-Dec-10 10:09 
General@SAKryukov : I am sorry,I didn't get what you're trying to c... Pin
Hiren Solanki27-Dec-10 21:30
memberHiren Solanki27-Dec-10 21:30 
General@JH64 : Thanks. Yes that's some excessive white space while ... Pin
Hiren Solanki27-Dec-10 21:28
memberHiren Solanki27-Dec-10 21:28 
GeneralHiren, unfortunately, adding "Also, it is not limited to nul... Pin
SAKryukov27-Dec-10 21:28
mvpSAKryukov27-Dec-10 21:28 
General@brad : I haven't said it's limited to NULL only I said it w... Pin
Hiren Solanki27-Dec-10 21:27
memberHiren Solanki27-Dec-10 21:27 
GeneralReason for my vote of 4 Nice. I will try to use ??. I think... Pin
JH6427-Dec-10 8:16
memberJH6427-Dec-10 8:16 
GeneralIt is called the null-coalescing (or coalesce) operator. It... Pin 7:35 7:35 
General@SledgeHammer01 : It was just reference from MSDN, Not copy ... Pin
Hiren Solanki23-Dec-10 19:33
memberHiren Solanki23-Dec-10 19:33 
SuggestionRe: @SledgeHammer01 : It was just reference from MSDN, Not copy ... Pin
Clifford Nelson7-Sep-12 15:29
memberClifford Nelson7-Sep-12 15:29 
GeneralRe: @SledgeHammer01 : It was just reference from MSDN, Not copy ... Pin
Hiren solanki7-Sep-12 19:50
memberHiren solanki7-Sep-12 19:50 
GeneralReason for my vote of 5 nice tip Pin
SChristmas23-Dec-10 6:32
memberSChristmas23-Dec-10 6:32 
GeneralReason for my vote of 2 copy and paste from MSDN Pin
SledgeHammer0123-Dec-10 6:11
memberSledgeHammer0123-Dec-10 6:11 

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