.net - What does "??" do in C#? -


this question has answer here:

i found new , interesting code in project. do, , how work?

memorystream stream = null; memorystream st = stream ?? new memorystream(); 

a ?? b

is shorthand 

if (a == null)      b else

or more precisely

a == null ? b :

so in verbose expansion, code equivalent to:

memorystream st; if(stream == null)     st = new memorystream(); else     st = stream;

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